TRANSLOCATION OF ELECTRICAL CHARGE DURING A SINGLE TURNOVER OF CYTOCHROME-C-OXIDASE

In cell respiration, cytochrome-c oxidase utilizes electrons from cata bolism to reduce O-2 to water. Energy is conserved as an electrochemic al proton gradient across the mitochondrial membrane, which drives the synthesis of ATP. Electrical charge translocation during the reaction of the reduced enzyme with O, takes place in two phases of identical amplitude. The first phase (tau(1) = 0.2 ms) occurs after an initial l ag, and appears to correspond to the transition from a peroxy to a fer ryl intermediate in the oxygen chemistry. The second phase (tau(2) = 2 .6 ms) matches the transition from the ferryl intermediate to the oxid ised enzyme. These findings define the kinetic linkage between the che mistry and the major events of proton pumping by the enzyme.