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Topical Collection "Feature Papers in Molecular Biophysics"

Editors

Prof. Dr. Ian A. Nicholls
Website
Collection Editor
Department of Chemistry and Biomedical Sciences, Linnaeus University, Kalmar, Sweden
Interests: biomimetic systems; complex mixture modelling and spectroscopic studies of biological; synthetic and hybrid systems
Special Issues and Collections in MDPI journals
Dr. Vladimir N. Uversky
grade Website SciProfiles
Collection Editor
Molecular Medicine, University of South Florida, Tampa, USA
Interests: intrinsically disordered proteins; protein folding; protein misfolding; partially folded proteins; protein aggregation; protein structure; protein function; protein stability; protein biophysics; protein bioinformatics; conformational diseases; protein–ligand interactions; protein–protein interactions; liquid-liquid phase transitions
Special Issues and Collections in MDPI journals

Topical Collection Information

Dear Colleagues,

As follows from the title, this Topical Collection “Feature Papers in Molecular Biophysics” aims to collect high quality research articles, short communications, and review articles in all the fields of molecular biophysics. Since the aim of this Topical Collection is to illustrate, through selected works, frontier research in molecular biophysics, we encourage Editorial Board Members of the Molecular Biophysics Section of the International Journal of Molecular Sciences to contribute papers reflecting the latest progress in their research field, or to invite relevant experts and colleagues to do so.

Topics include, but are not limited to:

  • molecular structure and dynamics
  • nucleic acid structure and dynamics
  • protein structure and dynamics
  • membrane structure and dynamics
  • biomimetic material structure and dynamics
  • molecular simulations
  • molecular modeling
  • single molecule biophysics
  • biophysical techniques in the study of biomacromolecular and biomimetic systems
  • biomolecular interactions
  • biomimetic material interactions
  • macromolecular structure determination or prediction
  • characterization of disordered proteins and their interactions
  • computational biophysics
  • bioinformatics
  • biophysical and computational approaches to drug design and development
  • advances in molecular biophysical methodologies as well as imaging techniques and data analysis
  • application of biophysical methods

Prof. Dr. Ian A. Nicholls
Dr. Vladimir N. Uversky
Guest Editors

Manuscript Submission Information

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Keywords

  • biophysics
  • molecular imprinting
  • molecular simulations
  • molecular structure
  • molecular dynamics
  • molecular mechanics
  • thermodynamics
  • biomolecular interactions
  • protein structure and folding
  • intrinsically disordered proteins
  • structure prediction
  • nucleic acid–protein interactions
  • protein–membrane interactions
  • protein–DNA interactions
  • posttranslational modifications
  • drug–receptor interactions
  • protein design
  • protein engineering
  • protein–ligand binding
  • transmembrane proteins
  • chaperones
  • enzymology
  • molecular recognition
  • molecular modeling
  • membrane dynamics
  • macromolecular structure and dynamics
  • DNA structure and dynamics
  • RNA structure
  • genome structure
  • structure–function relationships
  • ion channels
  • spectroscopic techniques
  • biomolecular NMR
  • inter-molecular interactions
  • X-ray crystallography
  • macromolecular crystallography
  • crystal thermodynamics
  • microcalorimetry
  • transient kinetic techniques
  • fluorescence imaging
  • single-molecule microscopy
  • statistical mechanics
  • computer simulations
  • computational modeling
  • molecular modeling

Published Papers (34 papers)

2020

Jump to: 2019

Open AccessArticle
Super-Resolution Live Cell Microscopy of Membrane-Proximal Fluorophores
Int. J. Mol. Sci. 2020, 21(19), 7099; https://doi.org/10.3390/ijms21197099 - 26 Sep 2020
Abstract
Here, we present a simple and robust experimental setup for the super-resolution live cell microscopy of membrane-proximal fluorophores, which is comparably easy to perform and to implement. The method is based on Structured Illumination Microscopy (SIM) with a switchable spatial light modulator (SLM) [...] Read more.
Here, we present a simple and robust experimental setup for the super-resolution live cell microscopy of membrane-proximal fluorophores, which is comparably easy to perform and to implement. The method is based on Structured Illumination Microscopy (SIM) with a switchable spatial light modulator (SLM) and exchangeable objective lenses for epi-illumination and total internal reflection fluorescence (TIRF) microscopy. While, in the case of SIM (upon epi-illumination), cell layers of about 1–2 µm in close proximity to the plasma membrane can be selected by software, layers in the 100 nm range are assessed experimentally by TIRF-SIM. To show the applicability of this approach, both methods are used to measure the translocation of the glucose transporter 4 (GLUT4) from intracellular vesicles to the plasma membrane upon stimulation by insulin or insulin-mimetic compounds, with a lateral resolution of around 100 nm and an axial resolution of around 200 nm. While SIM is an appropriate method to visualize the intracellular localization of GLUT4 fused with a green fluorescent protein, TIRF-SIM permits the quantitative evaluation of its fluorescence in the plasma membrane. These imaging methods are discussed in the context of fluorescence lifetime kinetics, providing additional data for the molecular microenvironment. Full article
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Open AccessReview
Zooming into the Dark Side of Human Annexin-S100 Complexes: Dynamic Alliance of Flexible Partners
Int. J. Mol. Sci. 2020, 21(16), 5879; https://doi.org/10.3390/ijms21165879 - 16 Aug 2020
Abstract
Annexins and S100 proteins form two large families of Ca2+-binding proteins. They are quite different both structurally and functionally, with S100 proteins being small (10–12 kDa) acidic regulatory proteins from the EF-hand superfamily of Ca2+-binding proteins, and with annexins [...] Read more.
Annexins and S100 proteins form two large families of Ca2+-binding proteins. They are quite different both structurally and functionally, with S100 proteins being small (10–12 kDa) acidic regulatory proteins from the EF-hand superfamily of Ca2+-binding proteins, and with annexins being at least three-fold larger (329 ± 12 versus 98 ± 7 residues) and using non-EF-hand-based mechanism for calcium binding. Members of both families have multiple biological roles, being able to bind to a large cohort of partners and possessing a multitude of functions. Furthermore, annexins and S100 proteins can interact with each other in either a Ca2+-dependent or Ca2+-independent manner, forming functional annexin-S100 complexes. Such functional polymorphism and binding indiscrimination are rather unexpected, since structural information is available for many annexins and S100 proteins, which therefore are considered as ordered proteins that should follow the classical “one protein–one structure–one function” model. On the other hand, the ability to be engaged in a wide range of interactions with multiple, often unrelated, binding partners and possess multiple functions represent characteristic features of intrinsically disordered proteins (IDPs) and intrinsically disordered protein regions (IDPRs); i.e., functional proteins or protein regions lacking unique tertiary structures. The aim of this paper is to provide an overview of the functional roles of human annexins and S100 proteins, and to use the protein intrinsic disorder perspective to explain their exceptional multifunctionality and binding promiscuity. Full article
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Open AccessArticle
Insights into the Effect of Curcumin and (–)-Epigallocatechin-3-Gallate on the Aggregation of Aβ(1–40) Monomers by Means of Molecular Dynamics
Int. J. Mol. Sci. 2020, 21(15), 5462; https://doi.org/10.3390/ijms21155462 - 30 Jul 2020
Cited by 1
Abstract
In this study, we compared the effects of two well-known natural compounds on the early step of the fibrillation process of amyloid-β (1–40), responsible for the formation of plaques in the brains of patients affected by Alzheimer’s disease (AD). The use of extensive [...] Read more.
In this study, we compared the effects of two well-known natural compounds on the early step of the fibrillation process of amyloid-β (1–40), responsible for the formation of plaques in the brains of patients affected by Alzheimer’s disease (AD). The use of extensive replica exchange simulations up to the µs scale allowed us to characterize the inhibition activity of (–)-epigallocatechin-3-gallate (EGCG) and curcumin (CUR) on unfolded amyloid fibrils. A reduced number of β-strands, characteristic of amyloid fibrils, and an increased distance between the amino acids that are responsible for the intra- and interprotein aggregations are observed. The central core region of the amyloid-β (Aβ(1–40)) fibril is found to have a high affinity to EGCG and CUR due to the presence of hydrophobic residues. Lastly, the free binding energy computed using the Poisson Boltzmann Surface Ares suggests that EGCG is more likely to bind to unfolded Aβ(1–40) fibrils and that this molecule can be a good candidate to develop new and more effective congeners to treat AD. Full article
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Open AccessArticle
Low-Dose Ionizing Radiation Modulates Microglia Phenotypes in the Models of Alzheimer’s Disease
Int. J. Mol. Sci. 2020, 21(12), 4532; https://doi.org/10.3390/ijms21124532 - 25 Jun 2020
Abstract
Alzheimer’s disease (AD) is the most common type of dementia. AD involves major pathologies such as amyloid-β (Aβ) plaques and neurofibrillary tangles in the brain. During the progression of AD, microglia can be polarized from anti-inflammatory M2 to pro-inflammatory M1 phenotype. The activation [...] Read more.
Alzheimer’s disease (AD) is the most common type of dementia. AD involves major pathologies such as amyloid-β (Aβ) plaques and neurofibrillary tangles in the brain. During the progression of AD, microglia can be polarized from anti-inflammatory M2 to pro-inflammatory M1 phenotype. The activation of triggering receptor expressed on myeloid cells 2 (TREM2) may result in microglia phenotype switching from M1 to M2, which finally attenuated Aβ deposition and memory loss in AD. Low-dose ionizing radiation (LDIR) is known to ameliorate Aβ pathology and cognitive deficits in AD; however, the therapeutic mechanisms of LDIR against AD-related pathology have been little studied. First, we reconfirm that LDIR (two Gy per fraction for five times)-treated six-month 5XFAD mice exhibited (1) the reduction of Aβ deposition, as reflected by thioflavins S staining, and (2) the improvement of cognitive deficits, as revealed by Morris water maze test, compared to sham-exposed 5XFAD mice. To elucidate the mechanisms of LDIR-induced inhibition of Aβ accumulation and memory loss in AD, we examined whether LDIR regulates the microglial phenotype through the examination of levels of M1 and M2 cytokines in 5XFAD mice. In addition, we investigated the direct effects of LDIR on lipopolysaccharide (LPS)-induced production and secretion of M1/M2 cytokines in the BV-2 microglial cells. In the LPS- and LDIR-treated BV-2 cells, the M2 phenotypic marker CD206 was significantly increased, compared with LPS- and sham-treated BV-2 cells. Finally, the effect of LDIR on M2 polarization was confirmed by detection of increased expression of TREM2 in LPS-induced BV2 cells. These results suggest that LDIR directly induced phenotype switching from M1 to M2 in the brain with AD. Taken together, our results indicated that LDIR modulates LPS- and Aβ-induced neuroinflammation by promoting M2 polarization via TREM2 expression, and has beneficial effects in the AD-related pathology such as Aβ deposition and memory loss. Full article
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Open AccessArticle
Mapping of CaM, S100A1 and PIP2-Binding Epitopes in the Intracellular N- and C-Termini of TRPM4
Int. J. Mol. Sci. 2020, 21(12), 4323; https://doi.org/10.3390/ijms21124323 - 17 Jun 2020
Abstract
Molecular determinants of the binding of various endogenous modulators to transient receptor potential (TRP) channels are crucial for the understanding of necessary cellular pathways, as well as new paths for rational drug designs. The aim of this study was to characterise interactions between [...] Read more.
Molecular determinants of the binding of various endogenous modulators to transient receptor potential (TRP) channels are crucial for the understanding of necessary cellular pathways, as well as new paths for rational drug designs. The aim of this study was to characterise interactions between the TRP cation channel subfamily melastatin member 4 (TRPM4) and endogenous intracellular modulators—calcium-binding proteins (calmodulin (CaM) and S100A1) and phosphatidylinositol 4, 5-bisphosphate (PIP2). We have found binding epitopes at the N- and C-termini of TRPM4 shared by CaM, S100A1 and PIP2. The binding affinities of short peptides representing the binding epitopes of N- and C-termini were measured by means of fluorescence anisotropy (FA). The importance of representative basic amino acids and their combinations from both peptides for the binding of endogenous TRPM4 modulators was proved using point alanine-scanning mutagenesis. In silico protein–protein docking of both peptides to CaM and S100A1 and extensive molecular dynamics (MD) simulations enabled the description of key stabilising interactions at the atomic level. Recently solved cryo-Electron Microscopy (EM) structures made it possible to put our findings into the context of the entire TRPM4 channel and to deduce how the binding of these endogenous modulators could allosterically affect the gating of TRPM4. Moreover, both identified binding epitopes seem to be ideally positioned to mediate the involvement of TRPM4 in higher-order hetero-multimeric complexes with important physiological functions. Full article
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Open AccessArticle
Hydrophobic Amino Acids as Universal Elements of Protein-Induced DNA Structure Deformation
Int. J. Mol. Sci. 2020, 21(11), 3986; https://doi.org/10.3390/ijms21113986 - 02 Jun 2020
Abstract
Interaction with the DNA minor groove is a significant contributor to specific sequence recognition in selected families of DNA-binding proteins. Based on a statistical analysis of 3D structures of protein–DNA complexes, we propose that distortion of the DNA minor groove resulting from interactions [...] Read more.
Interaction with the DNA minor groove is a significant contributor to specific sequence recognition in selected families of DNA-binding proteins. Based on a statistical analysis of 3D structures of protein–DNA complexes, we propose that distortion of the DNA minor groove resulting from interactions with hydrophobic amino acid residues is a universal element of protein–DNA recognition. We provide evidence to support this by associating each DNA minor groove-binding amino acid residue with the local dimensions of the DNA double helix using a novel algorithm. The widened DNA minor grooves are associated with high GC content. However, some AT-rich sequences contacted by hydrophobic amino acids (e.g., phenylalanine) display extreme values of minor groove width as well. For a number of hydrophobic amino acids, distinct secondary structure preferences could be identified for residues interacting with the widened DNA minor groove. These results hold even after discarding the most populous families of minor groove-binding proteins. Full article
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Open AccessArticle
Intrinsic Disorder in Tetratricopeptide Repeat Proteins
Int. J. Mol. Sci. 2020, 21(10), 3709; https://doi.org/10.3390/ijms21103709 - 25 May 2020
Cited by 1
Abstract
Among the realm of repeat containing proteins that commonly serve as “scaffolds” promoting protein-protein interactions, there is a family of proteins containing between 2 and 20 tetratricopeptide repeats (TPRs), which are functional motifs consisting of 34 amino acids. The most distinguishing feature of [...] Read more.
Among the realm of repeat containing proteins that commonly serve as “scaffolds” promoting protein-protein interactions, there is a family of proteins containing between 2 and 20 tetratricopeptide repeats (TPRs), which are functional motifs consisting of 34 amino acids. The most distinguishing feature of TPR domains is their ability to stack continuously one upon the other, with these stacked repeats being able to affect interaction with binding partners either sequentially or in combination. It is known that many repeat-containing proteins are characterized by high levels of intrinsic disorder, and that many protein tandem repeats can be intrinsically disordered. Furthermore, it seems that TPR-containing proteins share many characteristics with hybrid proteins containing ordered domains and intrinsically disordered protein regions. However, there has not been a systematic analysis of the intrinsic disorder status of TPR proteins. To fill this gap, we analyzed 166 human TPR proteins to determine the degree to which proteins containing TPR motifs are affected by intrinsic disorder. Our analysis revealed that these proteins are characterized by different levels of intrinsic disorder and contain functional disordered regions that are utilized for protein-protein interactions and often serve as targets of various posttranslational modifications. Full article
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Open AccessArticle
Characteristic Analysis of Homo- and Heterodimeric Complexes of Human Mitochondrial Pyruvate Carrier Related to Metabolic Diseases
Int. J. Mol. Sci. 2020, 21(9), 3403; https://doi.org/10.3390/ijms21093403 - 11 May 2020
Cited by 1
Abstract
Human mitochondrial pyruvate carriers (hMPCs), which are required for the uptake of pyruvate into mitochondria, are associated with several metabolic diseases, including type 2 diabetes and various cancers. Yeast MPC was recently demonstrated to form a functional unit of heterodimers. However, human MPC-1 [...] Read more.
Human mitochondrial pyruvate carriers (hMPCs), which are required for the uptake of pyruvate into mitochondria, are associated with several metabolic diseases, including type 2 diabetes and various cancers. Yeast MPC was recently demonstrated to form a functional unit of heterodimers. However, human MPC-1 (hMPC-1) and MPC-2 (hMPC-2) have not yet been individually isolated for their detailed characterization, in particular in terms of their structural and functional properties, namely, whether they exist as homo- or heterodimers. In this study, hMPC-1 and hMPC-2 were successfully isolated in micelles and they formed stable homodimers. However, the heterodimer state was found to be dominant when both hMPC-1 and hMPC-2 were present. In addition, as heterodimers, the molecules exhibited a higher binding capacity to both substrates and inhibitors, together with a larger structural stability than when they existed as homodimers. Taken together, our results demonstrated that the hetero-dimerization of hMPCs is the main functional unit of the pyruvate metabolism, providing a structural insight into the transport mechanisms of hMPCs. Full article
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Open AccessArticle
Data-Driven Modeling Identifies TIRAP-Independent MyD88 Activation Complex and Myddosome Assembly Strategy in LPS/TLR4 Signaling
Int. J. Mol. Sci. 2020, 21(9), 3061; https://doi.org/10.3390/ijms21093061 - 26 Apr 2020
Abstract
TLR4 complexes are essential for the initiation of the LPS-induced innate immune response. The Myddosome, which mainly contains TLR4, TIRAP, MyD88, IRAK1/4 and TRAF6 proteins, is regarded as a major complex of TLR4. Although the Myddosome has been well studied, a quantitative description [...] Read more.
TLR4 complexes are essential for the initiation of the LPS-induced innate immune response. The Myddosome, which mainly contains TLR4, TIRAP, MyD88, IRAK1/4 and TRAF6 proteins, is regarded as a major complex of TLR4. Although the Myddosome has been well studied, a quantitative description of the Myddosome assembly dynamics is still lacking. Furthermore, whether some unknown TLR4 complexes exist remains unclear. In this study, we constructed a SWATH-MS data-based mathematical model that describes the component assembly dynamics of TLR4 complexes. In addition to Myddosome, we suggest that a TIRAP-independent MyD88 activation complex is formed upon LPS stimulation, in which TRAF6 is not included. Furthermore, quantitative analysis reveals that the distribution of components in TIRAP-dependent and -independent MyD88 activation complexes are LPS stimulation-dependent. The two complexes compete for recruiting IRAK1/4 proteins. MyD88 forms higher-order assembly in the Myddosome and we show that the strategy to form higher-order assembly is also LPS stimulation-dependent. MyD88 forms a long chain upon weak stimulation, but forms a short chain upon strong stimulation. Higher-order assembly of MyD88 is directly determined by the level of TIRAP in the Myddosome, providing a formation mechanism for efficient signaling transduction. Taken together, our study provides an enhanced understanding of component assembly dynamics and strategies in TLR4 complexes. Full article
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Open AccessArticle
SAAMBE-3D: Predicting Effect of Mutations on Protein–Protein Interactions
Int. J. Mol. Sci. 2020, 21(7), 2563; https://doi.org/10.3390/ijms21072563 - 07 Apr 2020
Cited by 3
Abstract
Maintaining wild type protein–protein interactions is essential for the normal function of cell and any mutation that alter their characteristics can cause disease. Therefore, the ability to correctly and quickly predict the effect of amino acid mutations is crucial for understanding disease effects [...] Read more.
Maintaining wild type protein–protein interactions is essential for the normal function of cell and any mutation that alter their characteristics can cause disease. Therefore, the ability to correctly and quickly predict the effect of amino acid mutations is crucial for understanding disease effects and to be able to carry out genome-wide studies. Here, we report a new development of the SAAMBE method, SAAMBE-3D, which is a machine learning-based approach, resulting in accurate predictions and is extremely fast. It achieves the Pearson correlation coefficient ranging from 0.78 to 0.82 depending on the training protocol in benchmarking five-fold validation test against the SKEMPI v2.0 database and outperforms currently existing algorithms on various blind-tests. Furthermore, optimized and tested via five-fold cross-validation on the Cornell University dataset, the SAAMBE-3D achieves AUC of 1.0 and 0.96 on a homo and hereto-dimer test datasets. Another important feature of SAAMBE-3D is that it is very fast, it takes less than a fraction of a second to complete a prediction. SAAMBE-3D is available as a web server and as well as a stand-alone code, the last one being another important feature allowing other researchers to directly download the code and run it on their local computer. Combined all together, SAAMBE-3D is an accurate and fast software applicable for genome-wide studies to assess the effect of amino acid mutations on protein–protein interactions. The webserver and the stand-alone codes (SAAMBE-3D for predicting the change of binding free energy and SAAMBE-3D-DN for predicting if the mutation is disruptive or non-disruptive) are available. Full article
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Open AccessArticle
Distal Unfolding of Ferricytochrome c Induced by the F82K Mutation
Int. J. Mol. Sci. 2020, 21(6), 2134; https://doi.org/10.3390/ijms21062134 - 20 Mar 2020
Abstract
It is well known that axial coordination of heme iron in mitochondrial cytochrome c has redox-dependent stability. The Met80 heme iron axial ligand in the ferric form of the protein is relatively labile and can be easily replaced by alternative amino acid side [...] Read more.
It is well known that axial coordination of heme iron in mitochondrial cytochrome c has redox-dependent stability. The Met80 heme iron axial ligand in the ferric form of the protein is relatively labile and can be easily replaced by alternative amino acid side chains under non-native conditions induced by alkaline pH, high temperature, or denaturing agents. Here, we showed a redox-dependent destabilization induced in human cytochrome c by substituting Phe82—conserved amino acid and a key actor in cytochrome c intermolecular interactions—with a Lys residue. Introducing a positive charge at position 82 did not significantly affect the structure of ferrous cytochrome c but caused localized unfolding of the distal site in the ferric state. As revealed by 1H NMR fingerprint, the ferric form of the F82K variant had axial coordination resembling the renowned alkaline species, where the detachment of the native Met80 ligand favored the formation of multiple conformations involving distal Lys residues binding to iron, but with more limited overall structural destabilization. Full article
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Open AccessArticle
In Silico Insights into Protein–Protein Interaction Disruptive Mutations in the PCSK9-LDLR Complex
Int. J. Mol. Sci. 2020, 21(5), 1550; https://doi.org/10.3390/ijms21051550 - 25 Feb 2020
Cited by 1
Abstract
Gain-of-function mutations in PCSK9 (proprotein convertase subtilisin/kexin type 9) lead to reduced uptake of LDL (low density lipoprotein) cholesterol and, therefore, increased plasma LDL levels. However, the mechanism by which these mutants reduce LDL reuptake is not fully understood. Here, we have used [...] Read more.
Gain-of-function mutations in PCSK9 (proprotein convertase subtilisin/kexin type 9) lead to reduced uptake of LDL (low density lipoprotein) cholesterol and, therefore, increased plasma LDL levels. However, the mechanism by which these mutants reduce LDL reuptake is not fully understood. Here, we have used molecular dynamics simulations, MM/PBSA (Molecular Mechanics/Poisson–Boltzmann Surface Area) binding affinity calculations, and residue interaction networks, to investigate the protein–protein interaction (PPI) disruptive effects of two of PCSK9′s gain-of-function mutations, Ser127Arg and Asp374Tyr on the PCSK9 and LDL receptor complex. In addition to these PPI disruptive mutants, a third, non-interface mutation (Arg496Trp) is included as a positive control. Our results indicate that Ser127Arg and Asp374Tyr confer significantly improved binding affinity, as well as different binding modes, when compared to the wild-type. These PPI disruptive mutations lie between the EGF(A) (epidermal growth factor precursor homology domain A) of the LDL receptor and the catalytic domain of PCSK9 (Asp374Tyr) and between the prodomain of PCSK9 and the β-propeller of the LDL receptor (Ser127Arg). The interactions involved in these two interfaces result in an LDL receptor that is sterically inhibited from entering its closed conformation. This could potentially implicate the prodomain as a target for small molecule inhibitors. Full article
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Open AccessArticle
Mathematical Model of ATM Activation and Chromatin Relaxation by Ionizing Radiation
Int. J. Mol. Sci. 2020, 21(4), 1214; https://doi.org/10.3390/ijms21041214 - 12 Feb 2020
Cited by 1
Abstract
We propose a comprehensive mathematical model to study the dynamics of ionizing radiation induced Ataxia-telangiectasia mutated (ATM) activation that consists of ATM activation through dual mechanisms: the initiative activation pathway triggered by the DNA damage-induced local chromatin relaxation and the primary activation pathway [...] Read more.
We propose a comprehensive mathematical model to study the dynamics of ionizing radiation induced Ataxia-telangiectasia mutated (ATM) activation that consists of ATM activation through dual mechanisms: the initiative activation pathway triggered by the DNA damage-induced local chromatin relaxation and the primary activation pathway consisting of a self-activation loop by interplay with chromatin relaxation. The model is expressed as a series of biochemical reactions, governed by a system of differential equations and analyzed by dynamical systems techniques. Radiation induced double strand breaks (DSBs) cause rapid local chromatin relaxation, which is independent of ATM but initiates ATM activation at damage sites. Key to the model description is how chromatin relaxation follows when active ATM phosphorylates KAP-1, which subsequently spreads throughout the chromatin and induces global chromatin relaxation. Additionally, the model describes how oxidative stress activation of ATM triggers a self-activation loop in which PP2A and ATF2 are released so that ATM can undergo autophosphorylation and acetylation for full activation in relaxed chromatin. In contrast, oxidative stress alone can partially activate ATM because phosphorylated ATM remains as a dimer. The model leads to predictions on ATM mediated responses to DSBs, oxidative stress, or both that can be tested by experiments. Full article
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Open AccessArticle
Using the Gibbs Function as a Measure of Human Brain Development Trends from Fetal Stage to Advanced Age
Int. J. Mol. Sci. 2020, 21(3), 1116; https://doi.org/10.3390/ijms21031116 - 07 Feb 2020
Cited by 1
Abstract
We propose to use a Gibbs free energy function as a measure of the human brain development. We adopt this approach to the development of the human brain over the human lifespan: from a prenatal stage to advanced age. We used proteomic expression [...] Read more.
We propose to use a Gibbs free energy function as a measure of the human brain development. We adopt this approach to the development of the human brain over the human lifespan: from a prenatal stage to advanced age. We used proteomic expression data with the Gibbs free energy to quantify human brain’s protein–protein interaction networks. The data, obtained from BioGRID, comprised tissue samples from the 16 main brain areas, at different ages, of 57 post-mortem human brains. We found a consistent functional dependence of the Gibbs free energies on age for most of the areas and both sexes. A significant upward trend in the Gibbs function was found during the fetal stages, which is followed by a sharp drop at birth with a subsequent period of relative stability and a final upward trend toward advanced age. We interpret these data in terms of structure formation followed by its stabilization and eventual deterioration. Furthermore, gender data analysis has uncovered the existence of functional differences, showing male Gibbs function values lower than female at prenatal and neonatal ages, which become higher at ages 8 to 40 and finally converging at late adulthood with the corresponding female Gibbs functions. Full article
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Open AccessArticle
C-Terminal Domain of the Human Zinc Transporter hZnT8 Is Structurally Indistinguishable from Its Disease Risk Variant (R325W)
Int. J. Mol. Sci. 2020, 21(3), 926; https://doi.org/10.3390/ijms21030926 - 31 Jan 2020
Cited by 1
Abstract
The human zinc transporter 8 (hZnT8) plays important roles in the storage of insulin in the secretory vesicles of pancreatic β cells. hZnT8 consists of a transmembrane domain, with its N- and C-termini protruding into the cytoplasm. Interestingly, the exchange of arginine to [...] Read more.
The human zinc transporter 8 (hZnT8) plays important roles in the storage of insulin in the secretory vesicles of pancreatic β cells. hZnT8 consists of a transmembrane domain, with its N- and C-termini protruding into the cytoplasm. Interestingly, the exchange of arginine to tryptophan at position 325 in the C-terminal domain (CTD) increases the risk of developing type 2 diabetes mellitus (T2D). In the present study, the CTDs of hZnT8 (the wild-type (WT) and its disease risk variant (R325W)) were expressed, purified, and characterized in their native forms by biophysical techniques. The data reveal that the CTDs form tetramers which are stabilized by zinc binding, and exhibit negligible differences in their secondary structure content and zinc-binding affinities in solution. These findings provide the basis for conducting further structural studies aimed at unravelling the molecular mechanism underlying the increased susceptibility to develop T2D, which is modulated by the disease risk variant. Full article
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Open AccessReview
Integrated Computational Approaches and Tools for Allosteric Drug Discovery
Int. J. Mol. Sci. 2020, 21(3), 847; https://doi.org/10.3390/ijms21030847 - 28 Jan 2020
Cited by 9
Abstract
Understanding molecular mechanisms underlying the complexity of allosteric regulation in proteins has attracted considerable attention in drug discovery due to the benefits and versatility of allosteric modulators in providing desirable selectivity against protein targets while minimizing toxicity and other side effects. The proliferation [...] Read more.
Understanding molecular mechanisms underlying the complexity of allosteric regulation in proteins has attracted considerable attention in drug discovery due to the benefits and versatility of allosteric modulators in providing desirable selectivity against protein targets while minimizing toxicity and other side effects. The proliferation of novel computational approaches for predicting ligand–protein interactions and binding using dynamic and network-centric perspectives has led to new insights into allosteric mechanisms and facilitated computer-based discovery of allosteric drugs. Although no absolute method of experimental and in silico allosteric drug/site discovery exists, current methods are still being improved. As such, the critical analysis and integration of established approaches into robust, reproducible, and customizable computational pipelines with experimental feedback could make allosteric drug discovery more efficient and reliable. In this article, we review computational approaches for allosteric drug discovery and discuss how these tools can be utilized to develop consensus workflows for in silico identification of allosteric sites and modulators with some applications to pathogen resistance and precision medicine. The emerging realization that allosteric modulators can exploit distinct regulatory mechanisms and can provide access to targeted modulation of protein activities could open opportunities for probing biological processes and in silico design of drug combinations with improved therapeutic indices and a broad range of activities. Full article
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Open AccessCommunication
Unveiling the Molecular Basis of the Noonan Syndrome-Causing Mutation T42A of SHP2
Int. J. Mol. Sci. 2020, 21(2), 461; https://doi.org/10.3390/ijms21020461 - 10 Jan 2020
Cited by 1
Abstract
Noonan syndrome (NS) is a genetic disorder caused by the hyperactivation of the RAS-MAPK molecular pathway. About 50% of NS cases are caused by mutations affecting the SHP2 protein, a multi-domain phosphatase with a fundamental role in the regulation of the RAS-MAPK pathway. [...] Read more.
Noonan syndrome (NS) is a genetic disorder caused by the hyperactivation of the RAS-MAPK molecular pathway. About 50% of NS cases are caused by mutations affecting the SHP2 protein, a multi-domain phosphatase with a fundamental role in the regulation of the RAS-MAPK pathway. Most NS-causing mutations influence the stability of the inactive form of SHP2. However, one NS-causing mutation, namely T42A, occurs in the binding pocket of the N-SH2 domain of the protein. Here, we present a quantitative characterization of the effect of the T42A mutation on the binding of the N-terminal SH2 domain of SHP2 with a peptide mimicking Gab2, a fundamental interaction that triggers the activation of the phosphatase in the cellular environment. Our results show that whilst the T42A mutation does not affect the association rate constant with the ligand, it causes a dramatic increase of the affinity for Gab2. This effect is due to a remarkable decrease of the microscopic dissociation rate constant of over two orders of magnitudes. In an effort to investigate the molecular basis of the T42A mutation in causing Noonan syndrome, we also compare the experimental results with a more conservative variant, T42S. Our findings are discussed in the context of the structural data available on SHP2. Full article
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Open AccessArticle
Conformational Plasticity of the Active Site Entrance in E. coli Aspartate Transcarbamoylase and Its Implication in Feedback Regulation
Int. J. Mol. Sci. 2020, 21(1), 320; https://doi.org/10.3390/ijms21010320 - 03 Jan 2020
Cited by 2
Abstract
Aspartate transcarbamoylase (ATCase) has been studied for decades and Escherichia coli ATCase is referred as a “textbook example” for both feedback regulation and cooperativity. However, several critical questions about the catalytic and regulatory mechanisms of E. coli ATCase remain unanswered, especially about its [...] Read more.
Aspartate transcarbamoylase (ATCase) has been studied for decades and Escherichia coli ATCase is referred as a “textbook example” for both feedback regulation and cooperativity. However, several critical questions about the catalytic and regulatory mechanisms of E. coli ATCase remain unanswered, especially about its remote feedback regulation. Herein, we determined a structure of E. coli ATCase in which a key residue located (Arg167) at the entrance of the active site adopted an uncommon open conformation, representing the first wild-type apo-form E. coli ATCase holoenzyme that features this state. Based on the structure and our results of enzymatic characterization, as well as molecular dynamic simulations, we provide new insights into the feedback regulation of E. coli ATCase. We speculate that the binding of pyrimidines or purines would affect the hydrogen bond network at the interface of the catalytic and regulatory subunit, which would further influence the stability of the open conformation of Arg167 and the enzymatic activity of ATCase. Our results not only revealed the importance of the previously unappreciated open conformation of Arg167 in the active site, but also helped to provide rationalization for the mechanism of the remote feedback regulation of ATCase. Full article
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Open AccessArticle
In Situ Proteolysis Condition-Induced Crystallization of the XcpVWX Complex in Different Lattices
Int. J. Mol. Sci. 2020, 21(1), 308; https://doi.org/10.3390/ijms21010308 - 02 Jan 2020
Abstract
Although prevalent in the determination of protein structures; crystallography always has the bottleneck of obtaining high-quality protein crystals for characterizing a wide range of proteins; especially large protein complexes. Stable fragments or domains of proteins are more readily to crystallize; which prompts the [...] Read more.
Although prevalent in the determination of protein structures; crystallography always has the bottleneck of obtaining high-quality protein crystals for characterizing a wide range of proteins; especially large protein complexes. Stable fragments or domains of proteins are more readily to crystallize; which prompts the use of in situ proteolysis to remove flexible or unstable structures for improving crystallization and crystal quality. In this work; we investigated the effects of in situ proteolysis by chymotrypsin on the crystallization of the XcpVWX complex from the Type II secretion system of Pseudomonas aeruginosa. Different proteolysis conditions were found to result in two distinct lattices in the same crystallization solution. With a shorter chymotrypsin digestion at a lower concentration; the crystals exhibited a P3 hexagonal lattice that accommodates three complex molecules in one asymmetric unit. By contrast; a longer digestion with chymotrypsin of a 10-fold higher concentration facilitated the formation of a compact P212121 orthorhombic lattice with only one complex molecule in each asymmetric unit. The molecules in the hexagonal lattice have shown high atomic displacement parameter values compared with the ones in the orthorhombic lattice. Taken together; our results clearly demonstrate that different proteolysis conditions can result in the generation of distinct lattices in the same crystallization solution; which can be exploited in order to obtain different crystal forms of a better quality Full article
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2019

Jump to: 2020

Open AccessReview
Strategies for Molecular Imprinting and the Evolution of MIP Nanoparticles as Plastic Antibodies—Synthesis and Applications
Int. J. Mol. Sci. 2019, 20(24), 6304; https://doi.org/10.3390/ijms20246304 - 13 Dec 2019
Cited by 6
Abstract
Materials that can mimic the molecular recognition-based functions found in biology are a significant goal for science and technology. Molecular imprinting is a technology that addresses this challenge by providing polymeric materials with antibody-like recognition characteristics. Recently, significant progress has been achieved in [...] Read more.
Materials that can mimic the molecular recognition-based functions found in biology are a significant goal for science and technology. Molecular imprinting is a technology that addresses this challenge by providing polymeric materials with antibody-like recognition characteristics. Recently, significant progress has been achieved in solving many of the practical problems traditionally associated with molecularly imprinted polymers (MIPs), such as difficulties with imprinting of proteins, poor compatibility with aqueous environments, template leakage, and the presence of heterogeneous populations of binding sites in the polymers that contribute to high levels of non-specific binding. This success is closely related to the technology-driven shift in MIP research from traditional bulk polymer formats into the nanomaterial domain. The aim of this article is to throw light on recent developments in this field and to present a critical discussion of the current state of molecular imprinting and its potential in real world applications. Full article
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Open AccessArticle
Near-Infrared Markers based on Bacterial Phytochromes with Phycocyanobilin as a Chromophore
Int. J. Mol. Sci. 2019, 20(23), 6067; https://doi.org/10.3390/ijms20236067 - 02 Dec 2019
Cited by 1
Abstract
Biomarkers engineered on the basis of bacterial phytochromes with biliverdin IXα (BV) cofactor as a chromophore are increasingly used in cell biology and biomedicine, since their absorption and fluorescence spectra lie within the so-called optical “transparency window” of biological tissues. However, the quantum [...] Read more.
Biomarkers engineered on the basis of bacterial phytochromes with biliverdin IXα (BV) cofactor as a chromophore are increasingly used in cell biology and biomedicine, since their absorption and fluorescence spectra lie within the so-called optical “transparency window” of biological tissues. However, the quantum yield of BV fluorescence in these biomarkers does not exceed 0.145. The task of generating biomarkers with a higher fluorescence quantum yield remains relevant. To address the problem, we proposed the use of phycocyanobilin (PCB) as a chromophore of biomarkers derived from bacterial phytochromes. In this work, we characterized the complexes of iRFP713 evolved from RpBphP2 and its mutant variants with different location of cysteine residues capable of covalent tetrapyrrole attachment with the PCB cofactor. All analyzed proteins assembled with PCB were shown to have a higher fluorescence quantum yield than the proteins assembled with BV. The iRFP713/V256C and iRFP713/C15S/V256C assembled with PCB have a particularly high quantum yield of 0.5 and 0.45, which exceeds the quantum yield of all currently available near-infrared biomarkers. Moreover, PCB has 4 times greater affinity for iRFP713/V256C and iRFP713/C15S/V256C proteins compared to BV. These data establish iRFP713/V256C and iRFP713/C15S/V256C assembled with the PCB chromophore as promising biomarkers for application in vivo. The analysis of the spectral properties of the tested biomarkers allowed for suggesting that the high-fluorescence quantum yield of the PCB chromophore can be attributed to the lower mobility of the D-ring of PCB compared to BV. Full article
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Open AccessArticle
Intrinsic Disorder of the BAF Complex: Roles in Chromatin Remodeling and Disease Development
Int. J. Mol. Sci. 2019, 20(21), 5260; https://doi.org/10.3390/ijms20215260 - 23 Oct 2019
Abstract
The two-meter-long DNA is compressed into chromatin in the nucleus of every cell, which serves as a significant barrier to transcription. Therefore, for processes such as replication and transcription to occur, the highly compacted chromatin must be relaxed, and the processes required for [...] Read more.
The two-meter-long DNA is compressed into chromatin in the nucleus of every cell, which serves as a significant barrier to transcription. Therefore, for processes such as replication and transcription to occur, the highly compacted chromatin must be relaxed, and the processes required for chromatin reorganization for the aim of replication or transcription are controlled by ATP-dependent nucleosome remodelers. One of the most highly studied remodelers of this kind is the BRG1- or BRM-associated factor complex (BAF complex, also known as SWItch/sucrose non-fermentable (SWI/SNF) complex), which is crucial for the regulation of gene expression and differentiation in eukaryotes. Chromatin remodeling complex BAF is characterized by a highly polymorphic structure, containing from four to 17 subunits encoded by 29 genes. The aim of this paper is to provide an overview of the role of BAF complex in chromatin remodeling and also to use literature mining and a set of computational and bioinformatics tools to analyze structural properties, intrinsic disorder predisposition, and functionalities of its subunits, along with the description of the relations of different BAF complex subunits to the pathogenesis of various human diseases. Full article
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Open AccessCommunication
Multiplexed Competitive Screening of One-Bead-One-Component Combinatorial Libraries Using a ClonePix 2 Colony Sorter
Int. J. Mol. Sci. 2019, 20(20), 5119; https://doi.org/10.3390/ijms20205119 - 16 Oct 2019
Abstract
Screening solid-phase combinatorial libraries of bioactive compounds against fluorescently labeled target biomolecules is an established technology in ligand and drug discovery. Rarely, however, do screening methods include comprehensive strategies—beyond mere library blocking and competitive screening—to ensure binding selectivity of selected leads. This work [...] Read more.
Screening solid-phase combinatorial libraries of bioactive compounds against fluorescently labeled target biomolecules is an established technology in ligand and drug discovery. Rarely, however, do screening methods include comprehensive strategies—beyond mere library blocking and competitive screening—to ensure binding selectivity of selected leads. This work presents a method for multiplexed solid-phase peptide library screening using a ClonePix 2 Colony Picker that integrates (i) orthogonal fluorescent labeling for positive selection against a target protein and negative selection against competitor species with (ii) semi-quantitative tracking of target vs. competitor binding for every library bead. The ClonePix 2 technology enables global at-a-glance evaluation and customization of the parameters for bead selection to ensure high affinity and selectivity of the isolated leads. A case study is presented by screening a peptide library against green-labeled human immunoglobulin G (IgG) and red-labeled host cell proteins (HCPs) using ClonePix 2 to select HCP-binding ligands for flow-through chromatography applications. Using this approach, 79 peptide ligand candidates (6.6% of the total number of ligands screened) were identified as potential HCP-selective ligands, enabling a potential rate of >3,000 library beads screened per hour. Full article
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Open AccessArticle
Novel Genetic Markers for Early Detection of Elevated Breast Cancer Risk in Women
Int. J. Mol. Sci. 2019, 20(19), 4828; https://doi.org/10.3390/ijms20194828 - 28 Sep 2019
Abstract
This study suggests that two newly discovered variants in the MSH2 gene, which codes for a DNA mismatch repair (MMR) protein, can be associated with a high risk of breast cancer. While variants in the MSH2 gene are known to be linked with [...] Read more.
This study suggests that two newly discovered variants in the MSH2 gene, which codes for a DNA mismatch repair (MMR) protein, can be associated with a high risk of breast cancer. While variants in the MSH2 gene are known to be linked with an elevated cancer risk, the MSH2 gene is not a part of the standard kit for testing patients for elevated breast cancer risk. Here we used the results of genetic testing of women diagnosed with breast cancer, but who did not have variants in BRCA1 and BRCA2 genes. Instead, the test identified four variants with unknown significance (VUS) in the MSH2 gene. Here, we carried in silico analysis to develop a classifier that can distinguish pathogenic from benign mutations in MSH2 genes taken from ClinVar. The classifier was then used to classify VUS in MSH2 genes, and two of them, p.Ala272Val and p.Met592Val, were predicted to be pathogenic mutations. These two mutations were found in women with breast cancer who did not have mutations in BRCA1 and BRCA2 genes, and thus they are suggested to be considered as new bio-markers for the early detection of elevated breast cancer risk. However, before this is done, an in vitro validation of mutation pathogenicity is needed and, moreover, the presence of these mutations should be demonstrated in a higher number of patients or in families with breast cancer history. Full article
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Open AccessArticle
Low Energy Shock Wave Therapy Inhibits Inflammatory Molecules and Suppresses Prostatic Pain and Hypersensitivity in a Capsaicin Induced Prostatitis Model in Rats
Int. J. Mol. Sci. 2019, 20(19), 4777; https://doi.org/10.3390/ijms20194777 - 26 Sep 2019
Cited by 1
Abstract
The effect of low energy shock wave (LESW) therapy on the changes of inflammatory molecules and pain reaction was studied in a capsaicin (10 mM, 0.1 cc) induced prostatitis model in rats. Intraprostatic capsaicin injection induced a pain reaction, including closing of the [...] Read more.
The effect of low energy shock wave (LESW) therapy on the changes of inflammatory molecules and pain reaction was studied in a capsaicin (10 mM, 0.1 cc) induced prostatitis model in rats. Intraprostatic capsaicin injection induced a pain reaction, including closing of the eyes, hypolocomotion, and tactile allodynia, which effects were ameliorated by LESW treatment. LESW therapy (2Hz, energy flux density of 0.12 mJ/mm2) at 200 and 300 shocks significantly decreased capsaicin-induced inflammatory reactions, reflected by a reduction of tissue edema and inflammatory cells, COX-2 and TNF-α stained positive cells, however, the therapeutic effects were not observed at 100 shocks treated group. Capsaicin-induced IL-1β, COX-2, IL-6, caspase-1, and NGF upregulation on day 3 and 7, while NALP1 and TNF-α upregulation was observed on day 7. LESW significantly suppressed the expression of IL-1β, COX-2, caspase-1, NGF on day 3 and IL-1β, TNF-α, COX-2, NALP1, caspase-1, NGF expression on day 7 in a dose-dependent fashion. LESW has no significant effect on IL-6 expression. Intraprostatic capsaicin injection activates inflammatory molecules and induces prostatic pain and hypersensitivity, which effects were suppressed by LESW. These findings might be the potential mechanisms of LESW therapy for nonbacterial prostatitis in humans. Full article
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Open AccessArticle
Robust Sampling of Defective Pathways in Multiple Myeloma
Int. J. Mol. Sci. 2019, 20(19), 4681; https://doi.org/10.3390/ijms20194681 - 21 Sep 2019
Cited by 1
Abstract
We present the analysis of defective pathways in multiple myeloma (MM) using two recently developed sampling algorithms of the biological pathways: The Fisher’s ratio sampler, and the holdout sampler. We performed the retrospective analyses of different gene expression datasets concerning different aspects of [...] Read more.
We present the analysis of defective pathways in multiple myeloma (MM) using two recently developed sampling algorithms of the biological pathways: The Fisher’s ratio sampler, and the holdout sampler. We performed the retrospective analyses of different gene expression datasets concerning different aspects of the disease, such as the existing difference between bone marrow stromal cells in MM and healthy controls (HC), the gene expression profiling of CD34+ cells in MM and HC, the difference between hyperdiploid and non-hyperdiploid myelomas, and the prediction of the chromosome 13 deletion, to provide a deeper insight into the molecular mechanisms involved in the disease. Our analysis has shown the importance of different altered pathways related to glycosylation, infectious disease, immune system response, different aspects of metabolism, DNA repair, protein recycling and regulation of the transcription of genes involved in the differentiation of myeloid cells. The main difference in genetic pathways between hyperdiploid and non-hyperdiploid myelomas are related to infectious disease, immune system response and protein recycling. Our work provides new insights on the genetic pathways involved in this complex disease and proposes novel targets for future therapies. Full article
Open AccessArticle
Cooperative Binding of KaiB to the KaiC Hexamer Ensures Accurate Circadian Clock Oscillation in Cyanobacteria
Int. J. Mol. Sci. 2019, 20(18), 4550; https://doi.org/10.3390/ijms20184550 - 13 Sep 2019
Cited by 3
Abstract
The central oscillator generating cyanobacterial circadian rhythms comprises KaiA, KaiB, and KaiC proteins. Their interactions cause KaiC phosphorylation and dephosphorylation cycles over approximately 24 h. KaiB interacts with phosphorylated KaiC in competition with SasA, an output protein harboring a KaiB-homologous domain. Structural data [...] Read more.
The central oscillator generating cyanobacterial circadian rhythms comprises KaiA, KaiB, and KaiC proteins. Their interactions cause KaiC phosphorylation and dephosphorylation cycles over approximately 24 h. KaiB interacts with phosphorylated KaiC in competition with SasA, an output protein harboring a KaiB-homologous domain. Structural data have identified KaiB–KaiC interaction sites; however, KaiB mutations distal from the binding surfaces can impair KaiB–KaiC interaction and the circadian rhythm. Reportedly, KaiB and KaiC exclusively form a complex in a 6:6 stoichiometry, indicating that KaiB–KaiC hexamer binding shows strong positive cooperativity. Here, mutational analysis was used to investigate the functional significance of this cooperative interaction. Results demonstrate that electrostatic complementarity between KaiB protomers promotes their cooperative assembly, which is indispensable for accurate rhythm generation. SasA does not exhibit such electrostatic complementarity and noncooperatively binds to KaiC. Thus, the findings explain KaiB distal mutation effects, providing mechanistic insights into clock protein interplay. Full article
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Open AccessArticle
Cooperativity and Steep Voltage Dependence in a Bacterial Channel
Int. J. Mol. Sci. 2019, 20(18), 4501; https://doi.org/10.3390/ijms20184501 - 11 Sep 2019
Abstract
This paper reports on the discovery of a novel three-membrane channel unit exhibiting very steep voltage dependence and strong cooperative behavior. It was reconstituted into planar phospholipid membranes formed by the monolayer method and studied under voltage-clamp conditions. The behavior of the novel [...] Read more.
This paper reports on the discovery of a novel three-membrane channel unit exhibiting very steep voltage dependence and strong cooperative behavior. It was reconstituted into planar phospholipid membranes formed by the monolayer method and studied under voltage-clamp conditions. The behavior of the novel channel-former, isolated from Escherichia coli, is consistent with a linearly organized three-channel unit displaying steep voltage-gating (a minimum of 14 charges in the voltage sensor) that rivals that of channels in mammalian excitable membranes. The channels also display strong cooperativity in that closure of the first channel permits the second to close and closure of the second channel permits closure of the third. All three have virtually the same conductance and selectivity, and yet the first and third close at positive potentials whereas the second closes at negative potentials. Thus, is it likely that the second channel-former is oriented in the membrane in a direction opposite to that of the other two. This novel structure is named “triplin.” The extraordinary behavior of triplin indicates that it must have important and as yet undefined physiological roles. Full article
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Open AccessArticle
TRPM6 N-Terminal CaM- and S100A1-Binding Domains
Int. J. Mol. Sci. 2019, 20(18), 4430; https://doi.org/10.3390/ijms20184430 - 09 Sep 2019
Abstract
Transient receptor potential (TRPs) channels are crucial downstream targets of calcium signalling cascades. They can be modulated either by calcium itself and/or by calcium-binding proteins (CBPs). Intracellular messengers usually interact with binding domains present at the most variable TRP regions—N- and C-cytoplasmic termini. [...] Read more.
Transient receptor potential (TRPs) channels are crucial downstream targets of calcium signalling cascades. They can be modulated either by calcium itself and/or by calcium-binding proteins (CBPs). Intracellular messengers usually interact with binding domains present at the most variable TRP regions—N- and C-cytoplasmic termini. Calmodulin (CaM) is a calcium-dependent cytosolic protein serving as a modulator of most transmembrane receptors. Although CaM-binding domains are widespread within intracellular parts of TRPs, no such binding domain has been characterised at the TRP melastatin member—the transient receptor potential melastatin 6 (TRPM6) channel. Another CBP, the S100 calcium-binding protein A1 (S100A1), is also known for its modulatory activities towards receptors. S100A1 commonly shares a CaM-binding domain. Here, we present the first identified CaM and S100A1 binding sites at the N-terminal of TRPM6. We have confirmed the L520-R535 N-terminal TRPM6 domain as a shared binding site for CaM and S100A1 using biophysical and molecular modelling methods. A specific domain of basic amino acid residues (R526/R531/K532/R535) present at this TRPM6 domain has been identified as crucial to maintain non-covalent interactions with the ligands. Our data unambiguously confirm that CaM and S100A1 share the same binding domain at the TRPM6 N-terminus although the ligand-binding mechanism is different. Full article
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Open AccessArticle
Identifying Methylation Pattern and Genes Associated with Breast Cancer Subtypes
Int. J. Mol. Sci. 2019, 20(17), 4269; https://doi.org/10.3390/ijms20174269 - 31 Aug 2019
Cited by 6
Abstract
Breast cancer is regarded worldwide as a severe human disease. Various genetic variations, including hereditary and somatic mutations, contribute to the initiation and progression of this disease. The diagnostic parameters of breast cancer are not limited to the conventional protein content and can [...] Read more.
Breast cancer is regarded worldwide as a severe human disease. Various genetic variations, including hereditary and somatic mutations, contribute to the initiation and progression of this disease. The diagnostic parameters of breast cancer are not limited to the conventional protein content and can include newly discovered genetic variants and even genetic modification patterns such as methylation and microRNA. In addition, breast cancer detection extends to detailed breast cancer stratifications to provide subtype-specific indications for further personalized treatment. One genome-wide expression–methylation quantitative trait loci analysis confirmed that different breast cancer subtypes have various methylation patterns. However, recognizing clinically applied (methylation) biomarkers is difficult due to the large number of differentially methylated genes. In this study, we attempted to re-screen a small group of functional biomarkers for the identification and distinction of different breast cancer subtypes with advanced machine learning methods. The findings may contribute to biomarker identification for different breast cancer subtypes and provide a new perspective for differential pathogenesis in breast cancer subtypes. Full article
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Open AccessReview
Structure Determination by Single-Particle Cryo-Electron Microscopy: Only the Sky (and Intrinsic Disorder) is the Limit
Int. J. Mol. Sci. 2019, 20(17), 4186; https://doi.org/10.3390/ijms20174186 - 27 Aug 2019
Cited by 6
Abstract
Traditionally, X-ray crystallography and NMR spectroscopy represent major workhorses of structural biologists, with the lion share of protein structures reported in protein data bank (PDB) being generated by these powerful techniques. Despite their wide utilization in protein structure determination, these two techniques have [...] Read more.
Traditionally, X-ray crystallography and NMR spectroscopy represent major workhorses of structural biologists, with the lion share of protein structures reported in protein data bank (PDB) being generated by these powerful techniques. Despite their wide utilization in protein structure determination, these two techniques have logical limitations, with X-ray crystallography being unsuitable for the analysis of highly dynamic structures and with NMR spectroscopy being restricted to the analysis of relatively small proteins. In recent years, we have witnessed an explosive development of the techniques based on Cryo-electron microscopy (Cryo-EM) for structural characterization of biological molecules. In fact, single-particle Cryo-EM is a special niche as it is a technique of choice for the structural analysis of large, structurally heterogeneous, and dynamic complexes. Here, sub-nanometer atomic resolution can be achieved (i.e., resolution below 10 Å) via single-particle imaging of non-crystalline specimens, with accurate 3D reconstruction being generated based on the computational averaging of multiple 2D projection images of the same particle that was frozen rapidly in solution. We provide here a brief overview of single-particle Cryo-EM and show how Cryo-EM has revolutionized structural investigations of membrane proteins. We also show that the presence of intrinsically disordered or flexible regions in a target protein represents one of the major limitations of this promising technique. Full article
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Open AccessArticle
A New Approach for Spontaneous Silver Ions Immobilization onto Casein
Int. J. Mol. Sci. 2019, 20(16), 3864; https://doi.org/10.3390/ijms20163864 - 08 Aug 2019
Cited by 4
Abstract
The work presents the kinetic and isotherm studies of silver binding on casein, which was carried out using batch sorption technique. Moreover, the influence of light irradiation on the process was shown. In order to investigate the mechanism of metal ions sorption by [...] Read more.
The work presents the kinetic and isotherm studies of silver binding on casein, which was carried out using batch sorption technique. Moreover, the influence of light irradiation on the process was shown. In order to investigate the mechanism of metal ions sorption by casein the zero, pseudo-first order kinetics and Weber-Morris intra-particle diffusion as well as Langmuir and Freundlich isotherm models were used. Furthermore, to specify more precisely, the possible binding mechanism, the spectroscopic (FT-IR—Fourier Transform Infrared Spectroscopy, Raman), spectrometric (MALDI-TOF MS—Matrix-Assisted Laser Desorption/Ionization Time Of Flight Mass Spectrometry), microscopic (SEM—Scanning Electron Microscope, TEM/EDX—Transmission Electron Microscopy/Energy Dispersive X-ray detector) and thermal (TGA—Thermogravimetric Analysis, DTG—Derivative Thermogravimetry) analysis were performed. Kinetic study indicates that silver binding onto casein is a heterogeneous process with two main stages: initial rapid stage related to surface adsorption onto casein with immediate creation of silver nanoparticles and slower second stage of intraglobular diffusion with silver binding in chelated form (metalloproteins) or ion-exchange form. Spectroscopic techniques confirmed the binding process and MALDI-TOF MS analysis show the dominant contribution of the α-casein in the process. Moreover, the treatment of silver-casein complex by artificial physiological fluids was performed. Full article
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Open AccessCommunication
Non-Ionic Deep Eutectic Liquids: Acetamide–Urea Derived Room Temperature Solvents
Int. J. Mol. Sci. 2019, 20(12), 2857; https://doi.org/10.3390/ijms20122857 - 12 Jun 2019
Cited by 2
Abstract
A family of non-ionic deep eutectic liquids has been developed based upon mixtures of solid N-alkyl derivatives of urea and acetamide that in some cases have melting points below room temperature. The eutectic behaviour and physical characteristics of a series of eleven [...] Read more.
A family of non-ionic deep eutectic liquids has been developed based upon mixtures of solid N-alkyl derivatives of urea and acetamide that in some cases have melting points below room temperature. The eutectic behaviour and physical characteristics of a series of eleven eutectic mixtures are presented, along with a molecular dynamics study-supported hypothesis for the origin of the non-ideal mixing of these substances. Their use as solvents in applications ranging from natural product extraction to organic and polymer synthesis are demonstrated. Full article
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Open AccessArticle
CUBAN, a Case Study of Selective Binding: Structural Details of the Discrimination between Ubiquitin and NEDD8
Int. J. Mol. Sci. 2019, 20(5), 1185; https://doi.org/10.3390/ijms20051185 - 08 Mar 2019
Cited by 2
Abstract
The newly identified CUBAN (Cullin binding domain associating with NEDD8) domain recognizes both ubiquitin and the ubiquitin-like NEDD8. Despite the high similarity between the two molecules, CUBAN shows a clear preference for NEDD8, free and conjugated to cullins. We previously characterized the domain [...] Read more.
The newly identified CUBAN (Cullin binding domain associating with NEDD8) domain recognizes both ubiquitin and the ubiquitin-like NEDD8. Despite the high similarity between the two molecules, CUBAN shows a clear preference for NEDD8, free and conjugated to cullins. We previously characterized the domain structure, both alone and in complex with NEDD8. The results here reported are addressed to investigate the determinants that drive the selective binding of CUBAN towards NEDD8 and ubiquitin. The 15N HSQC NMR perturbation pattern of the labeled CUBAN domain, when combined with either NEDD8 or ubiquitin, shows a clear involvement of hydrophobic residues that characterize the early stages of these interactions. After a slow conformational selection step, hydrophobic and then neutral and polar interactions take place, which drive the correct orientation of the CUBAN domain, leading to differences in the recognition scheme of NEDD8 and ubiquitin. As a result, a cascade of induced fit steps seems to determine the structural preference shown for NEDD8 and therefore the basis of the selectivity of the CUBAN domain. Finally, molecular dynamics analysis was performed to determine by fluctuations the internal flexibility of the CUBAN/NEDD8 complex. We consider that our results, based on a structural investigation mainly focused on the early stages of the recognition, provide a fruitful opportunity to report the different behavior of the same protein with two highly similar binding partners. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Order, Disorder, BAF Complex, and Chromatin Remodeling
Authors: Nashwa El Hadidy and Vladimir N. Uversky

Title: In situ proteolysis condition-induced crystallization of the XcpVWX complex in different crystal lattice
Authors: Jerry Y. Zhang and Zongchao Jia
Affiliation: Department of Biomedical and Molecular Sciences, Queen's University

Title: Structural prerequisites for antimicrobial peptides to induce keratinocyte cell migration
Authors: G. Weindl, et al.

Title: Biophyiscal investigations into the interaction of synthetic anti-LPS peptides with the bacterial phospholipid membrane
Authors: P. Garidel, et al.

Title: Antiinflammatory mode of action of Pep19-2.5
Authors: Klaus Brandenburg, et al.

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