FIG. 2.

Reduction of Fe(III)-NTA by purified OmcA and MtrC. Time-dependent changes in the absorption band at 552 nm permitted the measurement of the oxidation of dithionite-reduced OmcA or MtrC (5 μM) upon rapid mixing with 150 μM Fe(III)-NTA (○), NaNO₂ (□), or NaNO₃ (▪), as indicated by an arrow. Transient decreases upon addition of Fe(III)-NTA were fitted to a model by assuming apparent rate constants of 1.5 ± 0.1 and 2.0 ± 0.2 s⁻¹ for OmcA and MtrC, respectively. The experimental conditions involved pH 7.0 and 25°C, as described in Materials and Methods. O.D. (552), optical density at 552 nm.