Article

Dissection of the ATP-induced conformational cycle of the molecular chaperone Hsp90.

Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Nature Structural &#38 Molecular Biology (impact factor: 12.71). 03/2009; 16(3):287-93. DOI:10.1038/nsmb.1565 pp.287-93
Source: PubMed

ABSTRACT The molecular chaperone heat-shock protein 90 (Hsp90) couples ATP hydrolysis to conformational changes driving a reaction cycle that is required for substrate activation. Recent structural analysis provided snapshots of the open and closed states of Hsp90, which mark the starting and end points of these changes. Using fluorescence resonance energy transfer (FRET), we dissected the cycle kinetically and identified the intermediates on the pathway. The conformational transitions are orders of magnitude slower than the ATP-hydrolysis step and thus are the limiting events during the reaction cycle. Furthermore, these structural changes can be tightly regulated by cochaperones, being completely inhibited by Sti1 or accelerated by Aha1. In fact, even in the absence of nucleotide, Aha1 induces Hsp90 rearrangements that speed up the conformational cycle. This comprehensive reconstitution of the Hsp90 cycle defines a controlled progression through distinct intermediates that can be modulated by conformation-sensitive cochaperones.

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Keywords

ATP-hydrolysis step
 
cochaperones
 
comprehensive reconstitution
 
conformation-sensitive cochaperones
 
conformational changes
 
conformational transitions
 
controlled progression
 
distinct intermediates
 
fluorescence resonance energy transfer
 
Hsp90 cycle defines
 
molecular chaperone heat-shock protein 90
 
reaction cycle
 
Recent structural analysis
 
Sti1
 
structural changes
 
substrate activation