title: Chemical and thermal unfolding of a global staphylococcal virulence regulator with a flexible C-terminal end.
abstract: SarA, a Staphylococcus aureus-specific dimeric protein, modulates the expression of numerous proteins including various virulence factors. Interestingly, S. aureus synthesizes multiple SarA paralogs seemingly for optimizing the expression of its virulence factors. To understand the domain structure/flexibility and the folding/unfolding mechanism of the SarA protein family, we have studied a recombinant SarA (designated rSarA) using various in vitro probes. Limited proteolysis of rSarA and the subsequent analysis of the resulting protein fragments suggested it to be a single-domain protein with a long, flexible C-terminal end. rSarA was unfolded by different mechanisms in the presence of different chemical and physical denaturants. While urea-induced unfolding of rSarA occurred successively via the formation of a dimeric and a monomeric intermediate, GdnCl-induced unfolding of this protein proceeded through the production of two dimeric intermediates. The surface hydrophobicity and the structures of the intermediates were not identical and also differed significantly from those of native rSarA. Of the intermediates, the GdnCl-generated intermediates not only possessed a molten globule-like structure but also exhibited resistance to dissociation during their unfolding. Compared to the native rSarA, the intermediate that was originated at lower GdnCl concentration carried a compact shape, whereas, other intermediates owned a swelled shape. The chemical-induced unfolding, unlike thermal unfolding of rSarA, was completely reversible in nature.
authors.affiliation: Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India.
authors.forename: Avisek
authors.initials: A
authors.lastname: Mahapa
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India.
authors.forename: Sukhendu
authors.initials: S
authors.lastname: Mandal
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India.
authors.forename: Anindya
authors.initials: A
authors.lastname: Biswas
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India.
authors.forename: Biswanath
authors.initials: B
authors.lastname: Jana
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India.
authors.forename: Soumitra
authors.initials: S
authors.lastname: Polley
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India.
authors.forename: Subrata
authors.initials: S
authors.lastname: Sau
authors.affiliation: Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India.
authors.forename: Keya
authors.initials: K
authors.lastname: Sau
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019791:Guanidine / Q000494:pharmacology; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D005810:Multigene Family; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013211:Staphylococcus aureus / Q000378:metabolism*; D013696:Temperature; D014508:Urea / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; C492107:SarA protein, Staphylococcus aureus; D014508:Urea; D019791:Guanidine
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