Abstract

The respiratory deficient nuclear mutant of Saccharomyces cerevisiae, N9-168, assigned to complementation group G95 was previously shown to lack subunit 9, one of the three mitochondrially encoded subunits of the Fo component of the mitochondrial ATPase. As a consequence of the structural defect in Fo, the ATPase activity of G95 mutants is not inhibited by rutamycin. The absence of subunit 9 in N9-168 has been correlated with a lower steady-state level of its mRNA and an increase in higher molecular weight precursor transcripts. These results suggest that the mutation is most likely to affect either translation of the oli1 mRNA or processing of the primary transcript. We have isolated a nuclear gene, designated ATP13, which complements the respiratory defect and restores rutamycin-sensitive ATPase in G95 mutants. Disruption of ATP13 induces a respiratory deficiency which is not complemented by G95 mutants. The nucleotide sequence of ATP13 indicates a primary translation product with an Mapp of 42,897. The protein has a basic amino terminal signal sequence that is cleaved upon import into mitochondria. No significant primary structure homology is detected with any protein in the most recent libraries.