Mutants of Saccharomyces cerevisiae with defective vacuolar function

Mutants of the yeast Saccharomyces cerevisiae that have a small vacuolar lysine pool were isolated and characterized. Mutant KL97 (lys1 slp1-1) and strain KL197-1A (slp1-1), a prototrophic derivative of KL97, did not grow well in synthetic medium supplemented with 10 mM lysine. Genetic studies indicated that the slp1-1 mutation (for small lysine pool) is recessive and is due to a single chromosomal mutation. Mutant KL97 shows the following pleiotropic defects in vacuolar functions. (i) It has small vacuolar pools for lysine, arginine, and histidine. (ii) Its growth is sensitive to lysine, histidine, Ca2+, heavy metal ions, and antibiotics. (iii) It has many small vesicles but no large central vacuole. (iv) It has a normal amount of the vacuolar membrane marker alpha-mannosidase but shows reduced activities of the vacuole sap markers proteinase A, proteinase B, and carboxypeptidase Y.