抄録
The yeast vacuole is a primary storage compartment, which also serves as a degradative organelle like the animal cell lysosome. The lumen of the vacuole is acidified by the vacuolar membrane H+-ATPase, the best-known member of the V-type ATPases of eukaryotic cells. This H+-ATPase is a multisubunit enzyme consisting of at least eight polypeptides with apparent molecular masses of 100, 69, 60, 42, 36, 32, 27, and 17, kDa. The genes (VMA) for seven of these subunits have been isolated, and their deletions have been constructed. These uma deletion mutants were defective in vacuolar acidification and showed common growth phenotypes : sensitive to pH and Ca2+ in the medium and deficient in respiration (Pet-). The screening for yeast calcium-sensitive mutants (cls) that are also Pet-have identified three novel genes, VMA 11-VMA 13. VMA 11 and VMA 13 encode putative subunits of the vacuolar membrane H+-ATPase. The VMA 12 gene product is not included in the enzyme but is required for the assembly and/or targeting of the enzyme.
