Catabolite inactivation of the yeast maltose transporter is due to proteolysis

Abstract
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 measured the cellular content of the transporter along this inactivation process. Loss of transport capacity was paralleled by a decrease of cross-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 catabolism of ethanol.