Enzymatic properties of the PMA2 plasma membrane-bound H(+)-ATPase of Saccharomyces cerevisiae.
The PMA1 H(+)-ATPase can be functionally replaced by its isoform PMA2 in the plasma membrane from Saccharomyces cerevisiae (Supply, P., Wach, A., Thinès-Sempoux, D., and Goffeau, A. (1993) J. Biol. Chem. 268, 19744-19752). From strains expressing either only PMA1 or PMA2, plasma membranes were isolated and their ATPase activities compared. Despite their 89% identity, the two enzymes differ as to the following parameters: activation by glucose and by Triton X-100, pH optimum, requirement for divalent cations, and inhibition by vanadate and by erythrosin B. More striking, the glucose-activated PMA2 enzyme displays a three to four times higher apparent affinity for MgATP, and maximal activity is reached with a 10-fold lower free Mg2+ concentration. These results suggest that the difference in PMA1 and PMA2 expression level is correlated with different H(+)-ATPase functions. The analysis of the PMA1 and PMA2 sequence alignment, compared with reported PMA1 mutations, points to a few residue substitutions as putative contributors to the observed kinetic changes.
Supply
P
P
Unité de Biochimie Physiologique, Université Catholique de Louvain, Louvain-La-Neuve, Belgium.
Wach
A
A
Goffeau
A
A
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000201:enzymology; D003902:Detergents / Q000494:pharmacology; D004923:Erythrosine / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D012044:Regression Analysis; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013012:Sorbitol / Q000494:pharmacology; D013816:Thermodynamics; D014638:Vanadates / Q000494:pharmacology
D003902:Detergents; D007527:Isoenzymes; D014638:Vanadates; D011092:Polyethylene Glycols; D013012:Sorbitol; D017830:Octoxynol; D006180:Proton-Translocating ATPases; D008274:Magnesium; D004923:Erythrosine