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EMBO J. 1995 Jul 17;14(14):3434-44.

Hsp78, a Clp homologue within mitochondria, can substitute for chaperone functions of mt-hsp70.

Author information

1
Institut für Physiologische Chemie der Universität München, Germany.

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.

PMID:
7628444
PMCID:
PMC394410
[Indexed for MEDLINE]
Free PMC Article

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