Identification of the essential yeast protein MIM17, an integral mitochondrial inner membrane protein involved in protein import.

We analyzed four Saccharomyces cerevisiae mutants defective in mitochondrial protein import and found that they are complemented by a novel gene encoding a 17 kDa protein. The protein is integrally located in the mitochondrial inner membrane and is termed MIM17. It shows significant homology to MIM23/Mas6p, a previously identified mitochondrial inner membrane protein required for the import of preproteins. Like MIM23, the precursor of MIM17 is synthesized without a presequence. A deletion of MIM17 is lethal. MIM17 thus joins the small group of mitochondrial proteins that are essential for the viability of yeast. We propose that MIM17 is an essential component of the preprotein import machinery of the mitochondrial inner membrane.