REGULATION OF THE EXPRESSION OF THE H-ATPASE GENES PMA1 AND PMA2 DURING GROWTH AND EFFECTS OF OCTANOIC-ACID IN SACCHAROMYCES-CEREVISIAE()

A peak of plasma membrane H+-ATPase activity during exponential growth is correlated with the expression of the PMA1 gene as monitored by me asurements of the beta-galactosidase activity from a PMA1-lacZ fusion. This peak of activity is also correlated to the content of the H+-ATP ase protein in yeast plasma membrane as shown by quantitative immunode tection. The PMA(2)-lacZ fusion assay indicates that the expression of the PMA2 gene is activated somewhat later during exponential phase bu t under all circumstances its activity remains at least 500-fold lower than that of the PMA1-lacZ fusion. A slight but significant stimulati on of ATPase activity by low concentrations of octanoic acid coincides with a decrease in the PMA1 gene expression. It is concluded that oct anoic acid stimulates de PMA1 ATPase activity by posttranslational mec hanisms.