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Special Issue "Bacterial Toxins: Structure–Function Relationship"

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Bacterial Toxins".

Deadline for manuscript submissions: 31 August 2018

Special Issue Editor

Guest Editor
Dr. Subramanyam Swaminathan

Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA
Website | E-Mail
Phone: 1-631-344-3187
Interests: bacterial toxins; botulinum neurotoxins; macromolecular complexes; protein crystallography; structure–function relationship; drug discovery; protein–protein interactions

Special Issue Information

Dear Colleagues:

Bacterial toxins are classified into two major types: Endotoxins and exotoxins. Endotoxins are specifically referred to as cell-associated toxins—non-protein lipopolysaccharides associated with the cell wall of Gram negative bacteria. They act at, or near, the bacterial growth site. Exotoxins are proteins secreted by bacteria and act at a site farther away from the secretion site. Enterotoxins, neurotoxins, cytotoxins, lysins (e.g., hemolysin), gangrene-producing toxins, etc., are some examples of bacterial endotoxins, the names also indicating the site of action of the toxin. Most of the exotoxins have enzymatic activity. Many bacterial toxins consist of two components, A and B subunits, and are called AB toxins. Subunit B is involved in binding to the target, a specific receptor and subunit A performs the catalytic action on a substrate. Diphtheria toxin and botulinum toxins are AB toxins which contain a translocation component in the binding subunit. Shiga and Cholera toxins are AB5 toxins indicating the presence of five binding subunits and one A subunit. Pore-forming toxins (PFT) form pores in the membrane for translocation of toxin component as in anthrax toxin and colicin or involved in ion movement disruption as in toxins. Interestingly, some toxins, such as botulinum toxins, have clinical applications.

This Special Issue will focus on exotoxins, their structures and biological function explained on the basis of their structure, the major emphasis being on structure– function relationships and counter measures to block the toxin activity. The structures of stand-alone individual protein toxins provide basic information about the fold and organization of the different components. However, their complexes with appropriate substrates and/or receptors are important since they help in both understanding the protein–protein interaction responsible for toxic activity and ways to disrupt the interaction to mitigate the effect of toxin. Recent developments in cryo-electron microscopy have made it possible to study large multi-protein complexes at near atomic resolution. This Special Issue will cover the expansive structural information available so far.

Dr. Subramanyam Swaminathan
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxins is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • bacterial toxins
  • three-dimensional structure
  • structure-function
  • toxin-receptor/substrate complexes
  • counter measures

Published Papers (2 papers)

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Research

Open AccessFeature PaperArticle Crystal Structure of Botulinum Neurotoxin A2 in Complex with the Human Protein Receptor SV2C Reveals Plasticity in Receptor Binding
Received: 6 March 2018 / Revised: 28 March 2018 / Accepted: 10 April 2018 / Published: 12 April 2018
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Abstract
Botulinum neurotoxins (BoNTs) are a family of highly dangerous bacterial toxins, with seven major serotypes (BoNT/A-G). Members of BoNTs, BoNT/A1 and BoNT/B1, have been utilized to treat an increasing number of medical conditions. The clinical trials are ongoing for BoNT/A2, another subtype of
[...] Read more.
Botulinum neurotoxins (BoNTs) are a family of highly dangerous bacterial toxins, with seven major serotypes (BoNT/A-G). Members of BoNTs, BoNT/A1 and BoNT/B1, have been utilized to treat an increasing number of medical conditions. The clinical trials are ongoing for BoNT/A2, another subtype of BoNT/A, which showed promising therapeutic properties. Both BoNT/A1 and BoNT/A2 utilize three isoforms of synaptic vesicle protein SV2 (SV2A, B, and C) as their protein receptors. We here present a high resolution (2.0 Å) co-crystal structure of the BoNT/A2 receptor-binding domain in complex with the human SV2C luminal domain. The structure is similar to previously reported BoNT/A-SV2C complexes, but a shift of the receptor-binding segment in BoNT/A2 rotates SV2C in two dimensions giving insight into the dynamic behavior of the interaction. Small differences in key residues at the binding interface may influence the binding to different SV2 isoforms, which may contribute to the differences between BoNT/A1 and BoNT/A2 observed in the clinic. Full article
(This article belongs to the Special Issue Bacterial Toxins: Structure–Function Relationship)
Figures

Graphical abstract

Open AccessArticle The Replacement of five Consecutive Amino Acids in the Cyt1A Protein of Bacillus thuringiensis Enhances its Cytotoxic Activity against Lung Epithelial Cancer Cells
Received: 13 February 2018 / Revised: 8 March 2018 / Accepted: 14 March 2018 / Published: 16 March 2018
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Abstract
Cyt1A protein is a cytolytic protein encoded by the cyt gene of Bacillus thuringiensis subsp. israelensis (Bti) as part of the parasporal crystal proteins produced during the sporulation. Cyt1A protein is unique compared to the other endotoxins present in these parasporal crystals. Unlike
[...] Read more.
Cyt1A protein is a cytolytic protein encoded by the cyt gene of Bacillus thuringiensis subsp. israelensis (Bti) as part of the parasporal crystal proteins produced during the sporulation. Cyt1A protein is unique compared to the other endotoxins present in these parasporal crystals. Unlike δ-endotoxins, Cyt1A protein does not require receptors to bind to the target cell and activate the toxicity. It has the ability to affect a broad range of cell types and organisms, due to this characteristic. Cyt1A has been recognized to not only target the insect cells directly, but also recruit other endotoxins by acting as receptors. Due to these mode of actions, Cyt1A has been studied for its cytolytic activity against human cancer cell lines, although not extensively. In this study, we report a novel Cyt1A protein produced by a Bti strain QBT229 isolated from Qatar. When tested for its cytotoxicity against lung cancer cells, this local strain showed considerably higher activity compared to that of the reference Bti and other strains tested. The possible reasons for such enhanced activity were explored at the gene and protein levels. It was evidenced that five consecutive amino acid replacements in the β8 sheet of the Cyt1A protein enhanced the cytotoxicity against the lung epithelial cancer cells. Such novel Cyt1A protein with high cytotoxicity against lung cancer cells has been characterized and reported through this study. Full article
(This article belongs to the Special Issue Bacterial Toxins: Structure–Function Relationship)
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