Figure 4.
Inactivation of the vacuolar protease Pep4p stabilizes Ena1p, but does not rescue growth of sro7Δ mutants on NaCl media. Time-course study of Ena1p-HA levels in (A) pep4Δ, sro7Δ and pep4Δ sro7Δ mutants and (B) sro7Δ, end4Δ sro7Δ, sec15-1 sro7Δ and vps27Δ sro7Δ mutants after exposure of cells to medium containing 0.5 M NaCl. Cell samples were withdrawn at time points indicated, and total protein extracts were analyzed for presence of Ena1p-HA by immunoblot analysis. The sec15-1 sro7Δ (ts) mutant was incubated at 34°C during salt treatment to inactivate Sec15-1p without causing total growth arrest. Immunoblot analysis was performed as described in Figure 3 and Materials and Methods. (C) Drop-test monitoring growth of sro7Δ, pep4Δ, vps27Δ, pep4Δ sro7Δ, and vps27Δ sro7Δ on YP and YP + 0.7 M NaCl plates. Tenfold dilutions of YP cultures of OD610 1.0 were spotted onto the plates, which were photographed after incubation for 48 h at 30°C.