Table 2.

Sulfane sulfur and copper in purified CO dehydrogenases which had received different treatments. E::km and F::km are the O. carboxidovorans mutants in coxE or coxF, respectively

Source of CODH	Treatment	S before (left) and after (right) the addition of Cu		Cu	Activity (μmol CO min−1 mg−1)
Wild type	A	1.95 ± 0.09	1.92 ± 0.11	8.07 ± 0.34	8.350
E::km	A	1.72 ± 0.16	1.98 ± 0.15	7.74 ± 0.22	8.617
	B	1.93 ± 0.13	0.87 ± 0.09	7.53 ± 0.63	5.113
	C	2.00 ± 0.02	1.12 ± 0.04	13.90 ± 0.38	3.016
F::km	A	1.47 ± 0.11	1.46 ± 0.26	8.85 ± 0.10	7.890
	B	1.58 ± 0.08	1.05 ± 0.11	8.40 ± 0.05	6.750
	C	1.40 ± 0.13	1.02 ± 0.35	11.60 ± 0.08	1.116

Treatments of CO dehydrogenases (5 mg ml⁻¹): A, for the removal of Cu and sulfane sulfur, anoxic enzymes were incubated with 5 mM KCN for 24 h and then treated with 5 mM sodium sulfide plus 5 mM sodium dithionite first followed by 150 µM Cu¹⁺(thiourea)₃; B, as isolated enzyme was treated with sodium sulfide and sodium dithionite and then with Cu¹⁺(thiourea)₃; C, as isolated enzyme was treated with Cu¹⁺-(thiourea)₃. The sulfide/dithionite assays were incubated in the dark at 37 °C for 10 h, and the Cu¹⁺-(thiourea)₃- assays at 37 °C for 2–4 h in the dark. After each treatment the enzyme solution was gel filtered on PD10 ready-to-use columns (Sephadex G25, GE Healthcare, Little Chalfont, UK). All figures are in mol per mol of CO dehydrogenase. Refer to Table 1, Fig. 6 and the “Methods” section for further details