Turnover of protein components of the plasma membrane of Saccharomyces cerevisiae.

The peptide composition of plasma membrane in Saccharomyces cerevisiae cells growing at different temperatures between 18 and 38 degrees C was studied using SDS-polyacrylamide gel electrophoresis. Stability of the proteins, both qualitative and quantitative, was observed at the tested temperatures. Treatment for 2 h with cycloheximide decreased by about 50% the amount of a 80 kDa membrane peptide at 18, 23, 28 and 33 degrees C, with no other apparent effects. At 38 degrees C the 80 kDa peptide was not affected by the presence of the drug. Addition of tunicamycin to cultures at concentrations partially inhibitory to growth caused a large accumulation of the 80 kDa peptide in the plasma membrane, which cycloheximide did not modify. Pulse-chase experiments indicated a low rate of turnover of total plasma membranes in cells growing at 18 and 28 degrees C. In contrast, at 38 degrees C about 50% of the radioactivity in plasma membranes disappeared after a 2 h chase. The 80 kDa protein band was the only one with significant differential decay.