Steps of the coupled charge translocation in the catalytic cycle of cytochrome c oxidase.

Cytochrome c oxidase (COX) terminates the respiratory chain in mitochondria and in plasmatic membrane of many aerobic bacteria. The enzyme reduces dioxygen molecule into water and the reaction is accompanied with generation of transmembrane difference of electric potentials. The energy conservation by COX is based on the vectorial organization of the chemical reaction due to substrate protons transfer from the negative phase into the active site to meet the electrons, coming from opposite side of the membrane. In addition, a half of free energy of redox-chemistry reaction is conserved through transmembrane proton pumping. Each of the reaction steps in the catalytic cycle of COX involves a sequence of coupled electron and proton transfer reaction. The time-resolved study of the coupled charge translocation during catalytic cycle of cytochrome c oxidase is reviewed. Based on many fascinating parallels between the mechanisms of COX and pigment-protein complex of photosystem II from oxygenic photosynthetic organisms, the data described could be used in the light-driven water-splitting process.