Eide D J, Bridgham J T, Zhao Z, Mattoon J R
Department of Biochemistry and Molecular Biology, University of Minnesota-Duluth 55812-2487.
Mol Gen Genet. 1993 Nov;241(3-4):447-56. doi: 10.1007/BF00284699.
Mutations in the GEF2 gene of the yeast Saccharomyces cerevisiae have pleiotropic effects. The gef2 mutants display a petite phenotype. These cells grow slowly on several different carbon sources utilized exclusively or primarily by respiration. This phenotype is suppressed by adding large amounts of iron to the growth medium. A defect in mitochondrial function may be the cause of the petite phenotype: the rate of oxygen consumption by intact gef2 cells and by mitochondrial fractions isolated from gef2 mutants was reduced 60%-75% relative to wild type. Cytochrome 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 by several divalent cations including Cu. We found that the cup5 mutation, causing Cu sensitivity, is allelic to gef2 mutations. The GEF2 gene was isolated, sequenced, and found to be identical to VMA3, the gene encoding the vacuolar H(+)-ATPase proteolipid subunit. These genetic and biochemical analyses demonstrate that the vacuolar H(+)-ATPase plays a previously unknown role in Cu detoxification, mitochondrial function, and iron metabolism.
酿酒酵母（Saccharomyces cerevisiae）的GEF2基因突变具有多效性。gef2突变体表现出小菌落表型。这些细胞在几种主要或仅通过呼吸作用利用的不同碳源上生长缓慢。通过向生长培养基中添加大量铁可以抑制这种表型。线粒体功能缺陷可能是小菌落表型的原因：完整的gef2细胞以及从gef2突变体中分离出的线粒体部分的耗氧率相对于野生型降低了60%-75%。gef2突变体中的细胞色素水平未受影响，这表明这些菌株中的血红素积累没有明显改变。gef2突变体对包括铜在内的几种二价阳离子的生长抑制也比野生型更敏感。我们发现，导致铜敏感性的cup5突变与gef2突变是等位基因。GEF2基因被分离、测序，结果发现它与VMA3相同，VMA3是编码液泡H(+)-ATPase蛋白脂质亚基的基因。这些遗传和生化分析表明，液泡H(+)-ATPase在铜解毒、线粒体功能和铁代谢中发挥了以前未知的作用。
