Michael Gebert,
Sandra G Schrempp,
Carola S Mehnert,
Anna K Heißwolf,
Silke Oeljeklaus, Raffaele Ieva,
Maria Bohnert,
Karina von der Malsburg,
Sebastian Wiese,
Thomas Kleinschroth,
Carola Hunte,
Helmut E Meyer,
Ilka Haferkamp,
Bernard Guiard,
Bettina Warscheid,
Nikolaus Pfanner,
Martin van der Laan
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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.
The Journal of Cell Biology 05/2012; 197(5):595-604. · 10.26 Impact Factor
