title: Measurement of the mitochondrial membrane potential and pH gradient from the redox poise of the hemes of the bc1 complex.
abstract: The redox potentials of the hemes of the mitochondrial bc(1) complex are dependent on the proton-motive force due to the energy transduction. This allows the membrane potential and pH gradient components to be calculated from the oxidation state of the hemes measured with multi-wavelength cell spectroscopy. Oxidation states were measured in living RAW 264.7 cells under varying electron flux and membrane potential obtained by a combination of oligomycin and titration with a proton ionophore. A stochastic model of bc(1) turnover was used to confirm that the membrane potential and redox potential of the ubiquinone pool could be measured from the redox poise of the b-hemes under physiological conditions assuming the redox couples are in equilibrium. The pH gradient was then calculated from the difference in redox potentials of cytochrome c and ubiquinone pool using the stochastic model to evaluate the ΔG of the bc(1) complex. The technique allows absolute quantification of the membrane potential, pH gradient, and proton-motive force without the need for genetic manipulation or exogenous compounds.
authors.affiliation: Department of Radiology, Dartmouth Medical School, Hanover, New Hampshire, USA.
authors.forename: N
authors.initials: N
authors.lastname: Kim
authors.forename: M O
authors.initials: MO
authors.lastname: Ripple
authors.forename: R
authors.initials: R
authors.lastname: Springett
mesh_terms: D025181:ATP Synthetase Complexes / Q000037:antagonists & inhibitors; D000818:Animals; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002460:Cell Line; D004579:Electron Transport / Q000187:drug effects; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D009840:Oligomycins / Q000494:pharmacology; D061209:Proton Ionophores / Q000494:pharmacology; D011522:Protons; D013269:Stochastic Processes
chemical_list: D009840:Oligomycins; D061209:Proton Ionophores; D011522:Protons; D006418:Heme; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D025181:ATP Synthetase Complexes; D014450:Electron Transport Complex III