FIG. 2.

Proteinase K treatment of Cu/Zn SODs. Samples were removed at the indicated time points and assayed for residual activity. The activity obtained in the untreated sample was considered 100% (0 min). Data are from representative but repeatable experiments. (A) ♦, SodCI; ⋄, SodCI monomer; ○, SodCII. Whole-cell extracts from strains producing a single SOD (JS460, JS680, or JS459) were diluted 10-fold in 20 mM Tris-HCl, pH 6.8, and incubated at 37°C with 0.25 mg/ml proteinase K. (B) ♦, SodCI; ⋄, SodCI monomer; ○, SodCII. Purified proteins at 0.01 mg/ml were treated with 0.2 mg/ml proteinase K. (C) •, SodCIII; □, E. coli SodC; ▵, B. abortus SodC. Whole-cell extracts from strains producing a single SOD (JS683, JS682, or JS681) were diluted 10-fold and treated with 0.25 mg/ml proteinase K.