title: Kinetic models of redox-coupled proton pumping.
abstract: Cytochrome c oxidase, the terminal enzyme of the respiratory chain, pumps protons across the inner mitochondrial membrane against an opposing electrochemical gradient by reducing oxygen to water. To explore the fundamental mechanisms of such redox-coupled proton pumps, we develop kinetic models at the single-molecule level consistent with basic physical principles. We demonstrate that pumping against potentials >150 mV can be achieved purely through electrostatic couplings, given an asymmetric arrangement of charge centers; however, nonlinear gates are essential for highly efficient real enzymes. The fundamental requirements for proton pumping identified here highlight a possible evolutionary origin of cytochrome c oxidase pumping. The general design principles are relevant also for other molecular machines and suggest future applications in biology-inspired fuel cells.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
authors.forename: Young C
authors.initials: YC
authors.lastname: Kim
authors.forename: Mårten
authors.initials: M
authors.lastname: Wikström
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hummer
mesh_terms: D003576:Electron Transport Complex IV; D007700:Kinetics; D008564:Membrane Potentials; D008956:Models, Chemical; D010084:Oxidation-Reduction; D017494:Proton Pumps / Q000378:metabolism*; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D017494:Proton Pumps; D003576:Electron Transport Complex IV