Genetics Change in pH

The mitochondrial ATP synthase is composed of multiple proteins, and some of these proteins are encoded by genes in the nucleus. One of these proteins is called S . A mutation in the S gene deletes 21 base pairs that are immediately 3’ to the start codon. The mutant S gene is transcribed and translated but the S protein remains in the cytoplasm. This mutant yeast cell can only grow anearobically, whereas wild type yeast can grow anaerobically or aerobically. Yeast grows as a haploid cell. In wild type cells in the presence of O2, the pH of the mitochondrial matrix is 8, but in cells with this mutant S gene, the pH is 7. Please explain these results.