FIGURE 3.

Dug1p, but not Dug2p, has functional peptidase domain. A and B, conserved glutamic acid residues that had a potential catalytic role were mutated to alanine; DUG1 wild type and DUG1 E171A mutant constructs in p416TEF vector were transformed into met15Δ dug1Δ strains of S. cerevisiae (A), and DUG2 wild type and DUG2 E586A mutant construct in p416TEF vector were transformed into met15Δ dug2Δ strains of S. cerevisiae and streaked on methionine or glutathione plates (B). C, DUG1, DUG2, and DUG2 M20A domain constructs in p416TEF vector were transformed into met15Δ dug1Δ strains of S. cerevisiae. Transformants were grown in minimal supplemented medium. Cells were harvested, washed, and resuspended to an A₆₀₀ = 2. Serial dilutions of A₆₀₀ = 0.2, 0.02, 0.002, and 0.0002 were made, and 5 μl of each dilution was spotted on minimal medium containing either methionine or glutathione as sulfur source. Plates were incubated at 30 °C for 3 days.