Role of the pathway through K(I-362) in proton transfer in cytochrome c oxidase from R. sphaeroides

The internal electron transfer reactions and proton-transfer coupled electron transfer without dioxygen in mutant enzymes, where I-362 and I-359 were substituted by KM(I-362) and TA(I-359), respectively, were examined in cytochrome c oxidase obtained from Rhodobacter sphaeroides. The results demonstrated that the electron transfer involving hemes a3 and a, having a time constant of approximately three microseconds, were not influenced in the mutant enzymes. On the other hand, the electron transfer between hemes a3 and a was reduced in the TA(I359) and KM(I-362) variants.