CATABOLITE INACTIVATION OF THE YEAST MALTOSE TRANSPORTER IS DUE TO PROTEOLYSIS

The maltose transport capacity of fermenting Saccharomyces cerevisiae rapidly decreases when protein synthesis is impaired. Using polyclonal antibodies against a recombinant maltose transporter-protein we measu red the cellular content of the transporter along this inactivation pr ocess. Loss of transport capacity was paralleled by a decrease of cros s-reacting material which suggests degradation of the transporter. We also show that in ammonium-starved cells the half-life of the maltose transporter is 1.3 h during catabolism of glucose and > 15 h during ca tabolism of ethanol.