Proton, Electron, and O2 transfer in Cytochrome c Oxidase

Sammanfattning: In mitochondria and aerobic bacteria energy conservation involves electron transfer through the membrane-bound protein of the respiratory chain to oxygen. Cytochrome c oxidase (CcO) catalyzes the reduction of oxygen to water. Part of the energy released in this reaction is used to pump protons across the membrane. The protons that are pumped, and those needed for reduction to water, are taken from the inside of the membrane. This helps to maintain an electrochemical potential over the membrane, which is necessary for the survival of the cell and is used for example to produce ATP.This work has been focused on the proton, electron and oxygen transfer in CcO from Rhodobacter sphaeroides. Results presented here show that there is a need for a specific O2-channel, due to structural rigidity of the area close to the catalytic site. In other parts of the enzyme regions that undergo redox-dependent structural changes were identified, and we proposed areas involved in controlling proton pumping and in forming the proton exit route.The results from investigating vectorial proton translocation defined the order and timing of proton uptake and release during a pumping-cycle. Indications from these results also suggested a mechanism by which CcO couples electron transfer and proton pumping, assuring that electrons are not transferred without simultaneous proton pumping.