Proton slippage in cytochrome c oxidase of Paracoccus denitrificans. Membrane-potential measurements with the two-subunit and three-subunit enzyme.
Isolated cytochrome c oxidase from Paracoccus denitrificans, containing either two or three subunits, was reconstituted into liposomes and the membrane potential was measured at different rates of respiration using a triphenylmethylphosponium bromide electrode. Both enzymes revealed a non-linear increase of the membrane potential with increasing respiratory rates. The ratios of the respiratory rates of the two proton pumps decreased with increasing membrane potential, suggesting slippage of proton pumping, as has been shown before with two cytochrome c oxidases from bovine heart, differing in H+/e- stoichiometries due to chemical modification [Steverding, D. & Kadenbach, B. (1991) J. Biol. Chem. 266, 8097-8101]. The data suggest that slippage of proton pumping represents an intrinsic property of cytochrome c oxidase associated with the two catalytic subunits, I and II.
Steverding
D
D
Fachbereich Chemie, Philipps-Universität, Marburg, Germany.
Köhnke
D
D
Ludwig
B
B
Kadenbach
B
B
D003576:Electron Transport Complex IV / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008081:Liposomes; D046911:Macromolecular Substances; D008564:Membrane Potentials; D010231:Paracoccus denitrificans / Q000201:enzymology*; D011510:Proteolipids / Q000378:metabolism; D011522:Protons
D008081:Liposomes; D046911:Macromolecular Substances; D011510:Proteolipids; D011522:Protons; C020485:proteoliposomes; D003576:Electron Transport Complex IV