Functional and physical interactions of components of the yeast mitochondrial inner-membrane import machinery (MIM).

The essential mitochondrial inner-membrane protein, Mim44, is involved in the translocation of preproteins across the mitochondrial inner membrane. Two other putative components of this protein-translocation system are the integral inner-membrane proteins, Mim23 and Mim17. Here, we present genetic evidence for functional co-operation of all three proteins. Furthermore, we show that Mim23 and Mim17 are associated in a protein complex that also contains two proteins of 55 kDa and 20 kDa. We speculate that this subcomplex forms the proteinaceous import channel of the inner-membrane which transiently interacts with a less abundant peripheral complex of Mim44 and mitochondrial heat-shock protein Hsp70.