Document Detail


The disaggregation activity of the mitochondrial ClpB homolog Hsp78 maintains Hsp70 function during heat stress.
MedLine Citation:
PMID:  16460754     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Molecular chaperones are important components of mitochondrial protein biogenesis and are required to maintain the organellar function under normal and stress conditions. We addressed the functional role of the Hsp100/ClpB homolog Hsp78 during aggregation reactions and its functional cooperation with the main mitochondrial Hsp70, Ssc1, in mitochondria of the yeast Saccharomyces cerevisiae. By establishing an aggregation/disaggregation assay in intact mitochondria we demonstrated that Hsp78 is indispensable for the resolubilization of protein aggregates generated by heat stress under in vivo conditions. The ATP-dependent disaggregation activity of Hsp78 was capable of reversing the preprotein import defect of a destabilized mutant form of Ssc1. This role in disaggregation of Ssc1 is unique for Hsp78, since the recently identified, Hsp70-specific chaperone Zim17 had no effect on the resolubilization reaction. We observed only a minor effect of the second mitochondrial Hsp100 family member Mcx1 on protein disaggregation. A "holding" activity of the mitochondrial Hsp70 system was a prerequisite for a successful resolubilization of aggregated proteins. We conclude that the protective role of Hsp78 in thermotolerance is mainly based on maintaining the molecular chaperone Ssc1 in a soluble and functional state.
Authors:
Birgit von Janowsky; Tamara Major; Karin Knapp; Wolfgang Voos
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-01-19
Journal Detail:
Title:  Journal of molecular biology     Volume:  357     ISSN:  0022-2836     ISO Abbreviation:  J. Mol. Biol.     Publication Date:  2006 Mar 
Date Detail:
Created Date:  2006-03-21     Completed Date:  2006-05-10     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  2985088R     Medline TA:  J Mol Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  793-807     Citation Subset:  IM    
Affiliation:
Institut für Biochemie und Molekularbiologie, Hermann-Herder-Str. 7, Universität Freiburg, 79104 Freiburg, Germany.
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MeSH Terms
Descriptor/Qualifier:
ATP-Dependent Proteases
Calcium-Transporting ATPases / genetics,  physiology
Endopeptidase Clp / chemistry*,  genetics
HSP70 Heat-Shock Proteins / genetics,  physiology*
Heat-Shock Proteins / chemistry*,  genetics,  physiology*
Hot Temperature
Mitochondria / enzymology,  metabolism*
Mitochondrial Proteins / physiology
Molecular Chaperones / genetics,  physiology
Mutation
Saccharomyces cerevisiae / enzymology,  genetics
Saccharomyces cerevisiae Proteins / chemistry*,  genetics,  physiology*
Serine Endopeptidases / physiology
Solubility
Chemical
Reg. No./Substance:
0/HSP70 Heat-Shock Proteins; 0/HSP78 protein, S cerevisiae; 0/Heat-Shock Proteins; 0/Mcx1 protein, S cerevisiae; 0/Mitochondrial Proteins; 0/Molecular Chaperones; 0/Saccharomyces cerevisiae Proteins; 0/Zim17 protein, S cerevisiae; EC 3.4.21.-/ATP-Dependent Proteases; EC 3.4.21.-/PIM1 protein, S cerevisiae; EC 3.4.21.-/Serine Endopeptidases; EC 3.4.21.92/Endopeptidase Clp; EC 3.6.1.8/Calcium-Transporting ATPases; EC 3.6.3.8/SSC1 protein, S cerevisiae

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