Theoretical study of role of H2O molecule on initial stage of reduction of O2 molecule in active site of cytochrome c oxidase

Mechanism of formation of [Fe–O–O–H, CuB] from [Fe–O–O, CuB] in active site of cytochrome c oxidase was theoretically investigated. It was found that the H2O molecule is hydrogen-bonded to both Tyr244 and His290, and is a key molecule to produce Fe–O–O–H. This H2O molecule plays a role as a carrier of a proton toward Fe–O–O to yield [Fe–O–O–H, CuB]. CuB atom is formally changed from cuprous state to cupric state through transportation of a proton by the H2O molecule. A new reaction mechanism, which we call ‘water-proton transport’ (WPT) mechanism, is proposed for the initial stage of reduction of the O2 molecule.