Fig. 4.

Expression of S711 phosphomimetic mutants increases susceptibility to oxidative stress. The yeast double mutant Δzwf1/Δidp2 cannot grow in the presence of H₂O₂ (17). Δzwf1 cells were or were not transformed with plasmids expressing WT or S711 IRP1 mutants to assess their ability to antagonize Idp2p activity through competition for isocitrate. Cells were grown in SD plus kanamycin media to mid-logarithmic phase and washed, and then serial 10-fold dilutions were spotted onto SC plus glycerol plates without (A) (11) or with the addition of 0.5 mM H₂O₂ (B) or 1 m MH₂O₂ (C). Immunoblotting gave relative levels (shown in parentheses) of IRP1 in Δzwf1 extracts from cells grown in liquid culture: WT (1), S711A (0.7), S711D (0.4), S711E (1.1), and S711T (1.5) (results not shown).