Paraquat and cadmium fail to stimulate the degradation of recently synthesized proteins in Δrpn10 and Δubc4Δubc5 strains and these strains contain higher amounts of oxidant-damaged proteins than WT during growth and after exposure to paraquat. (A) WT and mutants were grown exponentially at 30°C and treated with paraquat or cadmium for 90 min. Then cell proteins were labeled with 35S-Met for 5 min, and rates of degradation measured as in Fig. 2 A. (B) WT and mutants were grown exponentially, and a portion was exposed to paraquat for 90 min. The presence of carbonylated proteins in equal amounts of cell extracts was assayed by OxyBlot as in Fig. 3 A. To visualize oxidant damage in the control cells, approximately three times more protein was loaded than in cells treated with paraquat.
