OXA1P, WHICH IS REQUIRED FOR CYTOCHROME-C-OXIDASE AND ATP SYNTHASE COMPLEX-FORMATION, IS EMBEDDED IN THE MITOCHONDRIAL INNER MEMBRANE

We have previously isolated the yeast nuclear gene OXA1 and showed tha t Oxa1p is required for the formation of the cytochrome c oxidase and ATP synthase complexes, We have expressed Oxa1p in E. coli and shown t hat it is toxic and rapidly degraded. Nevertheless, a truncated protei n was successfully expressed and antibodies have been raised against t his truncated protein. These antibodies recognise a protein in mitocho ndrially enriched fractions. In vitro mitochondrial import experiments demonstrate that the import of Oxa1p is accompanied by the cleavage o f a long pre-sequence. Osmotic swelling and alkaline carbonate extract ion show that Oxa1p is an integral membrane protein located in the inn er membrane of mitochondria. The relationships between the sub-mitocho ndrial location and the function of Oxa1p are discussed.