THE VACUOLAR H-ATPASE OF SACCHAROMYCES-CEREVISIAE IS REQUIRED FOR EFFICIENT COPPER DETOXIFICATION, MITOCHONDRIAL-FUNCTION, AND IRON-METABOLISM()

Mutations in the GEF2 gene of the yeast Saccharomyces cerevisiae have pleiotropic effects. The gef2 mutants display a petite phenotype. Thes e cells grow slowly on several different carbon sources utilized exclu sively or primarily by respiration. This phenotype is suppressed by ad ding large amounts of iron to the growth medium. A defect in mitochond rial function may be the cause of the petite phenotype: the rate of ox ygen consumption by intact gef2 cells and by mitochondrial fractions i solated from gef2 mutants was reduced 60%-75% relative to wild type. C ytochrome levels were unaffected in gef2 mutants, indicating that heme accumulation is not significantly altered in these strains. The gef2 mutants were also more sensitive than wild type to growth inhibition b y several divalent cations including Cu. We found that the cup5 mutati on, causing Cu sensitivity, is allelic to gef2 mutations. The GEF2 gen e was isolated, sequenced, and found to be identical to VMA3, the gene encoding the vacuolar H+-ATPase proteolipid subunit. These genetic an d biochemical analyses demonstrate that the vacuolar H+-ATPase plays a previously unknown role in Cu detoxification, mitochondrial function, and iron metabolism.