Original Article

Mba1, a Novel Component of the Mitochondrial Protein Export Machinery of the Yeast Saccharomyces cerevisiae

Correspondence to: Johannes M. Herrmann, Institute for Physiological Chemistry, Goethestrasse 33, 80336 München, Germany. Tel:(49) 89-5996-265 Fax:(49) 89-5996-270 E-mail:hannes.herrmann{at}bio.med.uni-muenchen.de.

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

Key Words: mitochondria, protein translocation, Mba1, Oxa1, membrane insertion

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