FIGURE 1.

Nitrogen starvation induces vacuolar proteolysis of Ypk1. A, effects of a vacuolar protease inhibitor, PMSF, on nitrogen starvation-induced Ypk1 reduction. Logarithmically growing WT cells in SD medium supplemented with auxotrophic nutrients were starved of nitrogen (NS) in SD-N medium containing drug vehicle or 1 mm PMSF. Total cell lysates prepared at the indicated time points were resolved by SDS-PAGE and analyzed by Western blotting against Ypk1 (two bands) and a loading control, Pgk1. B, Ypk1 expression in nitrogen-starved WT and pep4Δ cells. Western blotting against Ypk1 and Pgk1 was performed as in A.