title: Electrochemistry suggests proton access from the exit site to the binuclear center in Paracoccus denitrificans cytochrome c oxidase pathway variants.
abstract: Two different pathways through which protons access cytochrome c oxidase operate during oxygen reduction from the mitochondrial matrix, or the bacterial cytoplasm. Here, we use electrocatalytic current measurements to follow oxygen reduction coupled to proton uptake in cytochrome c oxidase isolated from Paracoccus denitrificans. Wild type enzyme and site-specific variants with defects in both proton uptake pathways (K354M, D124N and K354M/D124N) were immobilized on gold nanoparticles, and oxygen reduction was probed electrochemically in the presence of varying concentrations of Zn(2+) ions, which are known to inhibit both the entry and the exit proton pathways in the enzyme. Our data suggest that under these conditions substrate protons gain access to the oxygen reduction site via the exit pathway.
authors: Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioélectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France.
authors: Thomas
authors: T
authors: Meyer
authors: Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioélectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France.
authors: Frédéric
authors: F
authors: Melin
authors: Institute of Biochemistry, Molecular Genetics, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
authors: Oliver-M H
authors: OM
authors: Richter
authors: Institute of Biochemistry, Molecular Genetics, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
authors: Bernd
authors: B
authors: Ludwig
authors: Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt/Main, Germany.
authors: Aimo
authors: A
authors: Kannt
authors: Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt/Main, Germany.
authors: Hanne
authors: H
authors: Müller
authors: Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt/Main, Germany.
authors: Hartmut
authors: H
authors: Michel
authors: Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioélectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France.
authors: Petra
authors: P
authors: Hellwig
mesh_terms: D004563:Electrochemistry / Q000379:methods*; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004800:Enzymes, Immobilized / Q000378:metabolism*; D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D010231:Paracoccus denitrificans / Q000201:enzymology*; D011522:Protons; D015032:Zinc / Q000494:pharmacology
chemical_list: D004800:Enzymes, Immobilized; D011522:Protons; D006046:Gold; D003576:Electron Transport Complex IV; D015032:Zinc
keywords: Bioelectrochemistry; Cytochrome c oxidase; Proton pumping; Zn(2+) inhibition