The Saccharomyces cerevisiae OXA1 gene is required for the correct assembly of cytochrome c oxidase and oligomycin-sensitive ATP synthase.

The nuclear gene OXA1 was first isolated in Saccharomyces cerevisiae and found to be required at a post-translational step in cytochrome c oxidase biogenesis, probably at the level of assembly. Mutations in OXA1 lead to a complete respiratory deficiency. The protein Oxa1p is conserved through evolution and a human homolog has been isolated by functional complementation of a yeast oxa1- mutant. In order to further our understanding of the role of Oxa1p, we have constructed two yeast strains in which the OXA1 open reading frame was almost totally deleted. Cytochrome spectra and enzymatic activity measurements show the absence of heme aa3 and of a cytochrome c oxido-reductase activity and dramatic decrease of the oligomycin sensitive ATPase activity. Analysis of the respiratory complexes in non-denaturing gels reveals that Oxa1p is necessary for the correct assembly of the cytochrome c oxidase and the ATP synthase complex.