Alterations of the α or β Subunits of the Mitochondria1 ATPase in Yeast Mutants

Abstract

Among 979 non-glycerol growers of the yeast Schizosaccharomyces pombe, 40 strains were deficient in the mitochondrial ATPase activity. Three of them exhibited an alteration in either the .alpha. or .beta. subunits of the F1ATPase. The .alpha. subunit was not immunodetected in the A23/13 mutant. The .beta. subunit was not immunodetected in the B59/1 mutant. The existence of these 2 mutants shows that the .alpha. and .beta. subunits can be present independently of each other in the inner mitochondrial membrane. The .beta. subunit of the mutant F25/28 had a slower electrophoretic mobility than that of the wild-type .beta. subunit. This phenotype indicates abnormal processing or specific modification of the .beta. subunit. All mutants showed reduced activities of the NADH-cytochrome c reductase and of the cytochrome oxidase and a decreased synthesis of cytochrome aa3 and cytochrome b. This pleiotropic phenotype apparently results from specific modifications in the mitochondrial protein synthesis. The mitochondrial synthesis of 4 polypeptides (3 cytochrome oxidase and 1 cytochrome b subunits) was markedly decreased or abent while 3 new polypeptides (MW = 54000, 20,000 and 15,000) were detected in all the mutants analyzed. This observation suggests that a functional F1ATPase is necessary for the correct synthesis and/or assembly of the mitochondrially made components of the cytochrome oxidase and cytochrome b complexes.