Figure 4.

Carbonylation, superoxide production, superoxide dismutase and catalase activity, and oxidative stress protein production in the mutT mutant compared with the wild-type strain. (A) Protein carbonyl levels in the wild-type (MG1655) and the mutT mutant strain. (B) Production of superoxide in the membrane vesicles (open bars), cytosolic fraction (gray bars), and total protein fraction (hatched bars) of a Φ(sodA′-′lacZ)49 Φ(sodB-kan)Δ2 and a Φ(sodA′-′lacZ)49 Φ(sodB-kan)Δ2 ΔmutT leu∷Tn10 strain. Each value represents the mean of triplicate determinations at two different protein concentrations and the variation between the measurements was <5%. (C) Catalase (open bars) and superoxide dismutase (gray bars) activity in crude extracts obtained from wild-type (Wt) and mutT mutants. Each value represents the mean of triplicate determinations at two different proteins concentration and the variation between the measurements was <10%. (D) Rate of synthesis of the oxidative stress protein Dps in the wild-type and mutT mutants. The autoradiograms show part of the two-dimensional gel with the Dps protein indicated with the arrow. The cells were pulse labeled during exponential growth (A₄₂₀ = 0.4 ± 0.05) with radioactive methionine as described previously (15).