Document Detail


The Co-chaperone Sba1 connects the ATPase reaction of Hsp90 to the progression of the chaperone cycle.
MedLine Citation:
PMID:  15364569     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The molecular chaperone Hsp90 mediates the ATP-dependent activation of a large number of proteins involved in signal transduction. During this process, Hsp90 was found to associate transiently with several accessory factors, such as p23/Sba1, Hop/Sti1, and prolyl isomerases. It has been shown that ATP hydrolysis triggers conformational changes within Hsp90, which in turn are thought to mediate conformational changes in the substrate proteins, thereby causing their activation. The specific role of the partner proteins in this process is unknown. Using proteins from Saccharomyces cerevisiae, we characterized the interaction of Hsp90 with its partner protein p23/Sba1. Our results show that the nucleotide-dependent N-terminal dimerization of Hsp90 is necessary for the binding of Sba1 to Hsp90 with an affinity in the nanomolar range. Two Sba1 molecules were found to bind per Hsp90 dimer. Sba1 binding to Hsp90 resulted in a decreased ATPase activity, presumably by trapping the hydrolysis state of Hsp90ATP. Ternary complexes of Hsp90Sba1 could be formed with the prolyl isomerase Cpr6, but not with Sti1. Based on these findings, we propose a model that correlates the ordered assembly of the Hsp90 co-chaperones with distinct steps of the ATP hydrolysis reaction during the chaperone cycle.
Authors:
Klaus Richter; Stefan Walter; Johannes Buchner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of molecular biology     Volume:  342     ISSN:  0022-2836     ISO Abbreviation:  J. Mol. Biol.     Publication Date:  2004 Oct 
Date Detail:
Created Date:  2004-09-14     Completed Date:  2004-11-01     Revised Date:  2009-12-11    
Medline Journal Info:
Nlm Unique ID:  2985088R     Medline TA:  J Mol Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1403-13     Citation Subset:  IM    
Affiliation:
Department für Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany.
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MeSH Terms
Descriptor/Qualifier:
Adenosine Triphosphatases / chemistry,  metabolism*
Cross-Linking Reagents
Cyclophilins / chemistry,  metabolism*
Dimerization
Fungal Proteins / chemistry,  metabolism*
HSP90 Heat-Shock Proteins / chemistry,  metabolism*
Heat-Shock Proteins
Hydrolysis
Models, Molecular
Molecular Chaperones / chemistry*,  metabolism*
Protein Binding
Saccharomyces cerevisiae / metabolism
Saccharomyces cerevisiae Proteins / chemistry*,  metabolism*
Chemical
Reg. No./Substance:
0/Cross-Linking Reagents; 0/Fungal Proteins; 0/HSP90 Heat-Shock Proteins; 0/Heat-Shock Proteins; 0/Molecular Chaperones; 0/SBA1 protein, S cerevisiae; 0/STI1 protein, S cerevisiae; 0/Saccharomyces cerevisiae Proteins; EC 3.6.1.-/Adenosine Triphosphatases; EC 5.2.1.-/Cyclophilins; EC 5.2.1.8/cyclophilin D

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