期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1991
卷号：88
期号：5
页码：1938-1942
DOI：10.1073/pnas.88.5.1938
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Yeast mutants in which genes encoding subunits of the vacuolar H(+)-ATPase were interrupted were assayed for their vacuolar ATPase and proton-uptake activities. The vacuoles from the mutants lacking subunits A (72 kDa), B (57 kDa), or c (proteolipid, 16 kDa) were completely inactive in these reactions. Immunological studies revealed that in the absence of each one of those subunits the catalytic sector was not assembled. Labeling with N,N'-[14C]dicyclohexylcarbodiimide showed the presence of the proteolipid in vacuoles of mutants in which genes encoding subunits of the catalytic sectors were interrupted. No labeling was detected in the mutant in which the gene encoding the proteolipid was interrupted. We conclude that of all the ATPase subunits only the proteolipid is assembled independently and it serves as a template for the assembly of the other subunits. Site-specific mutations were generated in the gene encoding the proteolipid. All of the drastic changes and replacements gave inactive proteins. About half of the single amino acid replacements gave active proteins. Replacing glutamic acid-137 by any of several amino acids, except for aspartic acid, abolished the activity of the enzyme. Other amino acids that may function in proton conductance were changed. It was found that glycine residues may replace amino acids with exchangeable protons.
