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Molecules 2017, 22(2), 244; doi:10.3390/molecules22020244

Structure and Conformational Properties of d-Glucose/d-Galactose-Binding Protein in Crowded Milieu

1
Institute of Cytology of the Russian Academy of Sciences, Laboratory of Structural Dynamics, Stability and Folding of Proteins, Tikhoretsky av. 4, St. Petersburg 197046, Russia
2
Saint-Petersburg Technological Institute (Technical University), Moskovsky av. 26, Saint-Petersburg 190013, Russia
3
Department of Biophysics, St. Petersburg State Polytechnical University, Polytechnicheskaya av. 29, St. Petersburg 195251, Russia
4
Department of Molecular Medicine and Byrd Alzheimer’s Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA
*
Authors to whom correspondence should be addressed.
Academic Editor: Derek J. McPhee
Received: 7 November 2016 / Revised: 26 January 2017 / Accepted: 29 January 2017 / Published: 6 February 2017
(This article belongs to the Section Natural Products)
View Full-Text   |   Download PDF [5946 KB, uploaded 7 February 2017]   |  

Abstract

Conformational changes of d-glucose/d-galactose-binding protein (GGBP) were studied under molecular crowding conditions modeled by concentrated solutions of polyethylene glycols (PEG-12000, PEG-4000, and PEG-600), Ficoll-70, and Dextran-70, addition of which induced noticeable structural changes in the GGBP molecule. All PEGs promoted compaction of GGBP and lead to the increase in ordering of its structure. Concentrated solutions of PEG-12000 and PEG-4000 caused GGBP aggregation. Although Ficoll-70 and Dextran-70 also promoted increase in the GGBP ordering, the structural outputs were different for different crowders. For example, in comparison with the GGBP in buffer, the intrinsic fluorescence spectrum of this protein was shifted to short-wave region in the presence of PEGs but was red-shifted in the presence of Ficoll-70 and Dextran-70. It was hypothesized that this difference could be due to the specific interaction of GGBP with the sugar-based polymers (Ficoll-70 and Dextran-70), indicating that protein can adopt different conformations in solutions containing molecular crowders of different chemical nature. It was also shown that all tested crowding agents were able to stabilize GGBP structure shifting the GGBP guanidine hydrochloride (GdnHCl)-induced unfolding curves to higher denaturant concentrations, but their stabilization capabilities did not depend on the hydrodynamic dimensions of the polymers molecules. Refolding of GGBP was complicated by protein aggregation in all tested solutions of crowding agents. The lowest yield of refolded protein was achieved in the highly concentrated solutions of PEG-12000. These data support the previous notion that the influence of macromolecular crowders on proteins is rather complex phenomenon that extends beyond the excluded volume effects. View Full-Text
Keywords: d-glucose/d-galactose-binding protein; macromolecular crowding; polymers; protein unfolding; protein folding; protein aggregation; intrinsic fluorescence; circular dichroism d-glucose/d-galactose-binding protein; macromolecular crowding; polymers; protein unfolding; protein folding; protein aggregation; intrinsic fluorescence; circular dichroism
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MDPI and ACS Style

Fonin, A.V.; Silonov, S.A.; Sitdikova, A.K.; Kuznetsova, I.M.; Uversky, V.N.; Turoverov, K.K. Structure and Conformational Properties of d-Glucose/d-Galactose-Binding Protein in Crowded Milieu. Molecules 2017, 22, 244.

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