Comparative effects of Saccharomyces cerevisiae cultivation under copper stress on the activity and kinetic parameters of plasma-membrane-bound H+-ATPases PMA1 and PMA2

Abstract

The major yeast plasma membrane H⁺-ATPase is encoded by the essential PMA ₁ gene. The PMA ₂ gene encodes an H⁺-ATPase that is functionally interchangeable with the one encoded by PMA ₁ , but it is expressed at a much lower level than the PMA ₁ gene and it is not essential. Using genetically manipulated strains of Saccharomyces cerevisiae that exclusively synthesize PMA₁ ATPase or PMA₂ ATPase under control of the PMA₁ promoter, we found that yeast cultivation under mild copper stress leads to a similar activation of PMA₂ and PMA₁ isoforms. At high inhibitory copper concentrations (close to the maximum that allowed growth), ATPase activity was reduced from maximal levels; this decrease in activity was less important for PMA₂ ATPase than for PMA₁ ATPase. The higher tolerance to high copper stress of the artificial strain synthesizing PMA₂ ATPase exclusively, as compared to that synthesizing solely PMA₁ ATPase, correlated both with the lower sensitivity of PMA₂ ATPase to the deleterious effects of copper in vivo and with its higher apparent affinity for MgATP, and suggests that plasma membrane H⁺-ATPase activity plays a role in yeast tolerance to copper.