THE IN-VIVO ACTIVATION OF SACCHAROMYCES-CEREVISIAE PLASMA-MEMBRANE H-ATPASE BY ETHANOL DEPENDS ON THE EXPRESSION OF THE PMA1 GENE, BUT NOT OF THE PMA2 GENE()

The expression of the PMA1 and PMA2 genes during Saccharomyces cerevis iae growth in medium with glucose plus increasing concentrations of et hanol was monitored by using PMA1-lacZ and PMA2-lacZ fusions and North ern blot hybridizations of total RNA probed with PMA1 gene. The presen ce of sub-lethal concentrations of ethanol enhanced the expression of PMA2 whereas it reduced the expression of PMA1. The inhibition of PMA1 expression by ethanol corresponded to a decrease in the content of pl asma membrane ATPase as quantified by immunoassays. Although an appare nt correspondence could exist between the increase of plasma membrane ATPase activity and the level of PMA2 expression, the maximal level of PMA2 expression remained about 200 times lower than PMA1. On the othe r hand, ethanol activated the plasmamembrane H+-ATPase activity from a strain expressing only the PMA1 ATPase but did not activate that from a strain expressing only the PMA2 ATPase. These results provide evide nce that in the presence of ethanol it is the PMA1 ATPase which is act ivated, probably by a post-translational mechanism and that the PMA2 A TPase is not involved.