Half-life of the Plasma Membrane ATPase and Its Activating System in Resting Yeast Cells

The stability of the yeast plasma membrane ATPase and its activating system has been investigated in resting Saccharomyces cerevisiae. The half-life of ATPase in the presence of glucose is about 11 h whereas in the presence of ethanol it is greater than 30 h. In the case of the ATPase activating system half-life values of about 5 and 14 h have been observed, respectively, in the presence of these substrates. These results indicate that, similarly to sugar transport systems, plasma membrane ATPase as well as its activating system are less stable than the bulk of proteins in this organism. The fact that all plasma membrane proteins so far examined show low half-life values suggests that a low stability could be a general characteristic of these proteins.