FIGURE 1.

Methane oxidation activity of apo membrane-bound M. capsulatus (Bath) pMMO after metal loading using two copper reconstitution methods. A, apo M. capsulatus (Bath) membranes were incubated with 1–5 eq of CuSO₄ per 100-kDa protomer. As-isolated crude membranes had an activity of 28 ± 2 nmol of methanol/min·mg (duroquinol) or 94 ± 7 nmol of methanol/min·mg (NADH). The maximum activity for both reductants occurred after addition of 2 eq of copper, and the activity recovered was 51% for duroquinol and 24% for NADH. B, apo membranes were incubated with 1, 2, 3, 4, 5 or 10 eq of copper per 100-kDa protomer as in A, but then was washed three times to remove excess copper prior to activity measurements. Copper ions bound per 100-kDa pMMO protomer after excess metal removal are reported on the x axis. As-isolated crude membranes had an activity of 27 ± 1 nmol of methanol/min·mg (duroquinol) and 139 ± 5 nmol of methanol/min·mg (NADH). The maximum activity recovered was 50% for duroquinol and 25% for NADH.