title: Elucidating the mechanism of substrate recognition by the bacterial Hsp90 molecular chaperone.
abstract: Hsp90 is a conformationally dynamic molecular chaperone known to promote the folding and activation of a broad array of protein substrates ("clients"). Hsp90 is believed to preferentially interact with partially folded substrates, and it has been hypothesized that the chaperone can significantly alter substrate structure as a mechanism to alter the substrate functional state. However, critically testing the mechanism of substrate recognition and remodeling by Hsp90 has been challenging. Using a partially folded protein as a model system, we find that the bacterial Hsp90 adapts its conformation to the substrate, forming a binding site that spans the middle and C-terminal domains of the chaperone. Cross-linking and NMR measurements indicate that Hsp90 binds to a large partially folded region of the substrate and significantly alters both its local and long-range structure. These findings implicate Hsp90's conformational dynamics in its ability to bind and remodel partially folded proteins. Moreover, native-state hydrogen exchange indicates that Hsp90 can also interact with partially folded states only transiently populated from within a thermodynamically stable, native-state ensemble. These results suggest a general mechanism by which Hsp90 can recognize and remodel native proteins by binding and remodeling partially folded states that are transiently sampled from within the native ensemble.
authors.affiliation: Department of Biochemistry, Brandeis University, Waltham, MA 02453, USA. Electronic address: tstreet@brandeis.edu.
authors.forename: Timothy O
authors.initials: TO
authors.lastname: Street
authors.affiliation: Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zeng
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Pellarin
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Bonomi
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA.
authors.forename: Andrej
authors.initials: A
authors.lastname: Sali
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.
authors.forename: Mark J S
authors.initials: MJ
authors.lastname: Kelly
authors.affiliation: Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA.
authors.forename: Feixia
authors.initials: F
authors.lastname: Chu
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA; The Howard Hughes Medical Institute, University of California, San Francisco, CA 94158, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Agard
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones
keywords: Hsp90; HtpG; chaperone; protein folding
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