FIGURE 4.

Additive phenotypes of nhx1Δ and ESCRT mutations. a, growth of the indicated single gene deletion strains (Δ) and double mutants with nhx1Δ (ΔΔ) was measured in yeast extract/peptone/dextrose (YPD) medium or in defined APG medium relative to isogenic BY4742 (WT). Note the severe growth impairment of the ΔΔ strains in APG medium. b, impaired growth of the nhx1Δvps20Δ double mutant shown in a was corrected to single mutant (vps20Δ) levels by the addition of KCl to APG medium (upper panel). Further addition of KCl resulted in acute growth inhibition. Growth of the double mutant was more sensitive to low and high pH (middle panel), with the addition of KCl (0.2 m) correcting the growth sensitivity at low pH to single mutant (vps20Δ) levels (lower panel). The average of triplicate experiments is shown. Similar results were observed for other ESCRT mutants shown in a. c, missorting of CPY to the extracellular medium was increased in double mutants. Serial dilutions of culture supernatant were applied to filters and probed with anti-CPY antibody as described under “Experimental Procedures.” IB, immunoblot.