Elucidating the Mechanism of Substrate Recognition by the Bacterial Hsp90 Molecular Chaperone

• Published in: Journal of molecular biology Vol. 426; no. 12; pp. 2393 - 2404
• Main Authors: Street, Timothy O., Zeng, Xiaohui, Pellarin, Riccardo, Bonomi, Massimiliano, Sali, Andrej, Kelly, Mark J.S., Chu, Feixia, Agard, David A.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 12-06-2014
• Subjects: Bacteria; Bacterial Proteins - metabolism; Binding Sites; chaperone; Hsp90; HSP90 Heat-Shock Proteins - metabolism; HtpG; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Chaperones - metabolism; Protein Binding; Protein Conformation; protein folding; HtpG; MS; SAXS; HX; Hsp90; CTD; chaperone; MD; LC; protein folding; SN; HSQC; NTD
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2014.04.001

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.
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•Bacterial Hsp90 middle and C-terminal domain flexibility is required for client recognition.•Bacterial Hsp90 causes local and long-range structural changes in a non-native client.•Bacterial Hsp90 can bind partially folded states that are transiently populated from the native ensemble.•We propose a general model of native client remodeling by Hsp90.