ATP22, a nuclear gene required for expression of the F0 sector of mitochondrial ATPase in Saccharomyces cerevisiae

Expression of the mitochondrial proton-translocating ATPase of Saccharomyces cerevisiae has been shown to depend on chaperones that target the F-1 and F-0 sectors of this inner membrane complex. Here we report a new gene, designated ATP22 ( reading frame YDR350C on chromosome IV), that provides an essential function in the assembly of F0. ATP22 was cloned by transformation of C208/L2, a strain previously assigned to complementation group G99 of a collection of respiration-defective nuclear pet mutants. C208/L2 and the other atp22 mutants have oligomycin-insensitive F-1-ATPase, suggesting that the lesion is confined to F-0. This is supported by the sedimentation properties of the mutant ATPase and results of immunochemical analysis of F-0 subunit polypeptides. Northern analysis of ATPase transcripts and in vivo pulse labeling of the mitochondrial translation products in the mutant indicate normal expression of subunits 6, 8, and 9, the three mitochondrial gene products of F-0. Atp22p therefore functions at a posttranslational stage in assembly of F-0. Localization studies indicate Atp22p to be a component of the mitochondrial inner membrane. Protease protection experiments further indicate that Atp22p faces the matrix side of the membrane where most of the ATPase proteins are located and assembled.