Metal concentration dependence of uptake by apo-MnSOD. (A) Fluorimetric metal uptake timecourses for recombinant human apo-MnSOD (25 μg/mL in 20 mM HEPES pH 8.2) at 37°C. 1, 50 μM CoCl2; 2, 1 mM CoCl2. (B) Fluorimetric metal uptake timecourses for recombinant Thermus thermophilus HB8 apo-MnSOD (50 μg/mL in 20 mM MOPS pH 7) at 65°C. 1, 100 μM CoCl2; 2, 2 mM CoCl2. (C) Fluorimetric metal uptake timecourses for Escherichia coli apo-MnSOD (50 μg/mL in 20 mM MOPS pH 7.6) at 37°C. 1, 24 μM CoCl2; 2, 240 μM CoCl2.