title: Substrate binding drives large-scale conformational changes in the Hsp90 molecular chaperone.
abstract: Hsp90 is a ubiquitous molecular chaperone. Previous structural analysis demonstrated that Hsp90 can adopt a large number of structurally distinct conformations; however, the functional role of this flexibility is not understood. Here we investigate the structural consequences of substrate binding with a model system in which Hsp90 interacts with a partially folded protein (Δ131Δ), a well-studied fragment of staphylococcal nuclease. SAXS measurements reveal that under apo conditions, Hsp90 partially closes around Δ131Δ, and in the presence of AMPPNP, Δ131Δ binds with increased affinity to Hsp90's fully closed state. FRET measurements show that Δ131Δ accelerates the nucleotide-driven open/closed transition and stimulates ATP hydrolysis by Hsp90. NMR measurements reveal that Hsp90 binds to a specific, highly structured region of Δ131Δ. These results suggest that Hsp90 preferentially binds a locally structured region in a globally unfolded protein, and this binding drives functional changes in the chaperone by lowering a rate-limiting conformational barrier.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158-2517, USA.
authors.forename: Timothy O
authors.initials: TO
authors.lastname: Street
authors.forename: Laura A
authors.initials: LA
authors.lastname: Lavery
authors.forename: David A
authors.initials: DA
authors.lastname: Agard
mesh_terms: D000266:Adenylyl Imidodiphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D005454:Fluorescence Polarization; D031541:Fluorescence Resonance Energy Transfer; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008836:Micrococcal Nuclease / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D001426:Bacterial Proteins; C074510:HSP82 protein, S cerevisiae; D018841:HSP90 Heat-Shock Proteins; D010446:Peptide Fragments; D029701:Saccharomyces cerevisiae Proteins; C066720:HtpG protein, bacteria; D000266:Adenylyl Imidodiphosphate; D008836:Micrococcal Nuclease