Mba1, a novel component of the mitochondrial protein export machinery of the yeast Saccharomyces cerevisiae

The biogenesis of mitochondria requires the integration of many proteins in to the inner membrane from the matrix side, The inner membrane protein Oral plays an important role in this process. We identified Mba1 as a second mi tochondrial component that is required for efficient protein insertion. Lik e Oral, Mba1 specifically interacts both with mitochondrial translation pro ducts and with conservatively sorted, nuclear-encoded proteins during their integration into the inner membrane. Oral and Mba1 overlap in function and substrate specificity, but both can act independently of each other. We co nclude that Mba1 is part of the mitochondrial protein export machinery and represents the first component of a novel Oxa1-independent insertion pathwa y into the mitochondrial inner membrane.