IDENTIFICATION OF A 3RD YEAST MITOCHONDRIAL TOM PROTEIN WITH TETRATRICO PEPTIDE REPEATS

The mitochondrial outer membrane contains a protein complex with at le ast eight subunits responsible for recognition and translocation of pr eproteins synthesized in the cytosol, Two subunits, the receptors Tom2 0 and Tom70, contain tetratrico peptide repeats that are thought to be involved in protein-protein interactions, We have identified Saccharo myces cerevisiae Tom72, a new Tom protein expressed at a low level, To m72 is homologous to Tom70, including seven tetratrico peptide repeats , Tom72 is targeted to the mitochondrial outer membrane, forms a large domain exposed to the cytosol and loosely associates with the translo case complex of the outer membrane, These results suggest that Tom72 r epresents a ninth, weakly expressed component of the preprotein transl ocase of the mitochondrial outer membrane.