Abstract
Hsp78 is a Clp homologue within mitochondria of Saccharomyces cerevisiae. Deletion of HSP78 does not cause any detectable changes in wild type cells, but results in a petite phenotype in the ssc1-3 mutant strain carrying a temperature-sensitive allele of mt-hsp70. When overexpressed in the ssc1-3 mutant strain, hsp78 suppresses the defect in mitochondrial protein import under permissive conditions in vitro and interacts directly with newly imported polypeptide chains. As a molecular chaperone, hsp78 prevents the aggregation of misfolded proteins in the matrix of mitochondria under conditions of impaired mt-hsp70 function. However, unlike misfolded proteins associated with mt-hsp70, hsp78-bound polypeptides are not efficiently degraded by the ATP-dependent PIM1 protease. Thus, hsp78 can partially substitute for mt-hsp70 functions in the assembly of mitochondria and may be part of a salvage pathway if mt-hsp70 is limiting.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Biological Transport
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Calcium-Binding Proteins / metabolism
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Carrier Proteins / metabolism
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Cloning, Molecular
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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HSP70 Heat-Shock Proteins / metabolism*
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Heat-Shock Proteins / genetics
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Heat-Shock Proteins / metabolism*
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Membrane Proteins / metabolism
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Mitochondria / metabolism*
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Mitochondrial Membrane Transport Proteins*
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Mitochondrial Precursor Protein Import Complex Proteins
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Molecular Sequence Data
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Mutation
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Peptides / metabolism
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Protein Folding
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins*
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Temperature
Substances
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Calcium-Binding Proteins
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Carrier Proteins
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Fungal Proteins
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HSP70 Heat-Shock Proteins
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HSP78 protein, S cerevisiae
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Heat-Shock Proteins
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Membrane Proteins
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Mitochondrial Membrane Transport Proteins
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Mitochondrial Precursor Protein Import Complex Proteins
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Peptides
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Saccharomyces cerevisiae Proteins
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TIM44 protein, S cerevisiae