Mutational studies with Atp12p, a protein required for assembly of the mitochondrial F1-ATPase in yeast....

The Atp12p protein of Saccharomyces cerevisiae is required for assembly of the F1 moiety of the mitochondrial ATP synthase. The current work has used mutant forms of Atp12p in an effort to learn about amino acids and/or domains that are important for the action of the protein. In one set of studies, the mutant atp12 genes were cloned and sequenced from 13 independent isolates of chemically mutagenized yeast. Of the 10 different mutant alleles that were identified, 9 (8 nonsense and 1 frameshift) lead to the early termination of the protein. A single missense mutation that substitutes lysine for Glu-289 was identified in two of the atp12 strains. Analysis of several Atp12p variants, each with different substitutions at Glu-289, showed that the functional activity of Atp12p is compromised when non-acidic residues are introduced at position 289 in the sequence. In other work, deletion analysis led to the assignment of two domains in Atp12p; the functional domain of the protein was mapped to the sequence between Gln-181 and Val-306, and a structural domain (Asp-307 through Gln-325) was identified that confers Atp12p the ability to oligomerize with other proteins in mitochondria.