Biogenesis of mitochondria 36

Summary The isolation and characterisation of a mutant affecting the assembly of mitochondrial ATPase is reported. The mutation confers resistance to oligomycin and venturicidin and sensitivity of growth on nonfermentable substrates to low temperature (19°). Genetic analysis indicates that the phenotype is due to a single mutation located on the mitochondrial DNA which is probably allelic with the independently isolated oligomycin resistance mutation oli1-r].Growth of the mutant at the non-restrictive temperature (28°) yields mitochondria in which the ATPase appears more sensitive to oligomycin than that of the sensitive parental strain. However, when the enzyme is isolated free from the influence of the membrane strong resistance to oligomycin is evident. These data suggest that the component responsible for the oligomycin resistance of the ATPase is part of or subject to interaction with the mitochondrial inner membrane.Measurements of the ATPase content of mitochondria indicate that ATPase production is impaired during growth at 19° C. In addition, studies of the maximum inhibition of mitochondrial ATPase activity by high concentrations of oligomycin suggest a selective lesion in ATPase assembly at low temperature. The nett result is that during growth at 19° only about 10% of the normal level of ATPase is produced of which less than half is membrane integrated and thus capable of oxidative energy production.We propose that the mutation affects a mitochondrially synthesised membrane sector peptide of the ATPase which defines the interaction of F₁ ATPase with specific environments on the mitochondrial inner membrane.