Effect of copper on the digestion pattern of T. maritima CopA WT, ΔNMBD, and CXXC proteins. SDS–PAGE was performed as described in Experimental Procedures. Purified proteins (0.5 mg/mL) of CopA WT (a) and the mutants (b and c) were incubated with 0.5 mg/mL papain at 50 °C in the presence of 1 mM BCS without copper (lanes 2−7) or with 10 μM CuCl2 (lanes 8−13), as indicated at the bottom. The numbers on top of the gels refer to minutes of digestion: lane 1, 0 min; lanes 2 and 8, 2 min; lanes 3 and 9, 5 min; lanes 4 and 10, 10 min; lanes 5 and 11, 15 min; lanes 6 and 12, 20 min; and lanes 7 and 13, 30 min.