The growth of mdp1/rsp5 mutants of Saccharomyces cerevisiae is affected bymutations in the ATP-binding domain of the plasma membrane H+-ATPase

Mutations in the PMA1 gene, encoding plasma membrane H+-ATPase, were isolat ed that are able to suppress the temperature sensitivity (ts) phenotype of mdp1 mutations located in RSP5, the ubiquitin-protein ligase gene. The mdp1 mutants were previously found to change the mitochondrial/cytosolic distri bution of Mod5p-I, the tRNA modifying enzyme, and to affect fluid phase end ocytosis. The data presented reveal that mdp1 mutants are also pH sensitive , and hypersensitive to hygromycin B and paromomycin. The ts phenotype, hyg romycin B and paromomycin sensitivity are suppressed by pmal-t, but the pH sensitivity, the effect of mdp1 on Mod5p-I cytoplasmic/mitochondrial locali zation and endocytosis are not. Characterization of pmal-t revealed the sub stitution of amino acid G(653)V in the ATP-binding domain of the H+-ATPase. Our results indicate that Rsp5 ubiquitin-protein ligase may also influence , in addition to protein distribution, the functioning of plasma membrane H +-ATPase and the response of cells to stress. (C) 2000 Published by Elsevie r Science B.V. All rights reserved.