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J Cell Biol. 2012 May 28;197(5):595-604. doi: 10.1083/jcb.201110047. Epub 2012 May 21.

Mgr2 promotes coupling of the mitochondrial presequence translocase to partner complexes.

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1
Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Fakultät für Biologie, Funktionelle Proteomik, Universität Freiburg, 79104 Freiburg, Germany.

Abstract

Many mitochondrial proteins are synthesized with N-terminal presequences in the cytosol. The presequence translocase of the inner mitochondrial membrane (TIM23) translocates preproteins into and across the membrane and associates with the matrix-localized import motor. The TIM23 complex consists of three core components and Tim21, which interacts with the translocase of the outer membrane (TOM) and the respiratory chain. We have identified a new subunit of the TIM23 complex, the inner membrane protein Mgr2. Mitochondria lacking Mgr2 were deficient in the Tim21-containing sorting form of the TIM23 complex. Mgr2 was required for binding of Tim21 to TIM23(CORE), revealing a binding chain of TIM23(CORE)-Mgr2/Tim21-respiratory chain. Mgr2-deficient yeast cells were defective in growth at elevated temperature, and the mitochondria were impaired in TOM-TIM23 coupling and the import of presequence-carrying preproteins. We conclude that Mgr2 is a coupling factor of the presequence translocase crucial for cell growth at elevated temperature and for efficient protein import.

PMID:
22613836
PMCID:
PMC3365495
DOI:
10.1083/jcb.201110047
[Indexed for MEDLINE]
Free PMC Article
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