THE MATURE AEP2 GENE-PRODUCT OF SACCHAROMYCES-CEREVISIAE, REQUIRED FOR THE EXPRESSION OF SUBUNIT-9 OF ATP SYNTHASE, IS A 58-KDA MITOCHONDRIAL PROTEIN

The nucleotide sequence of the yeast nuclear AEP2 gene, required for t he expression of the mitochondrial DNA-encoded subunit 9 of ATP syntha se, predicts a primary translation product of 67.5 kDa. The ATP13 gene is allelic to AEP2 but was reported to encode a protein of about 42 k Da in size. We thus investigated genetically and biochemically the siz e of the AEP2 gene product. Genetic complementation assays using 3' tr uncated AEP2 genes, here shows that function is abolished by the remov al of only 32 amino acids from the C-terminus of the predicted protein product, Cell-free translation of AEP2 produces a 64 kDa polypeptide (consistent with the AEP2 sequence) which is imported into mitochondri a and processed to a 58 kDa product by the removal of a presequence of about 50 amino acids.