A kluyveromyces lactis gene homologue to AAC2 complements the Saccaromyces cerevisiae op1 mutation.

A mutation (op1) in the Saccharomyces cerevisiae AAC2 gene, which codes for the most abundant ADP/ATP carrier isoform, results in lack of mitochondrial-dependent growth and in an as yet unexplained petite-negative phenotype. A gene from the petite-negative yeast Kluyveromyces lactis has been isolated by complementing in multicopy the op1 mutation of S. cerevisiae. This gene, designated KIAAC, can complement the petite-negative phenotype of op1 as well as its inability to grow on nonfermentable carbon sources. KIAAC contains a 915-base pair open reading frame coding for a protein of 305 amino acids which shows a high degree of identity to AAC2. The K. lactis ADP/ATP carrier also shares identity with other known ADP/ATP carrier sequences. In particular, the degree of identity of KIAAC is higher with the Neurospora crassa carrier (80.1%) than with AAC1 (76.6%). The nucleotide sequence upstream of the KIAAC coding region was found to contain a long DNA segment with no coding potential, but presenting features of highly regulated promoter sequences.