A B3LYP study on the mechanism of second H2O formation in a fully reduced cytochrome c oxidase

The mechanism of second H2O formation in fully reduced cytochrome c oxidase is examined by sequential additions of one electron and two protons to a [Fe(IV)O, Cu(II)] compound II, which is the final intermediate of first H2O formation. It is found that the addition of one electron induces the concerted proton–electron transfer from the CuB to FeO moieties with no energy barriers. The H2O molecule coordinating to the Cu atom is a key molecule for the proton transfer from the CuB moiety to the FeO and/or Fe–OH moieties. It is also found from the results in previous and the present works that one can realize the reduction process of dioxygen by fully reduced cytochrome c oxidase.