The unusual redox properties of C-type oxidases.
Cytochrome cbb3(also known as C-type) oxidases belong to the family of heme-copper terminal oxidases which couple at the end of the respiratory chain the reduction of molecular oxygen into water and the pumping of protons across the membrane. They are expressed most often at low pressure of O2and they exhibit a low homology of sequence with the cytochrome aa3(A-type) oxidases found in mitochondria. Their binuclear active site comprises a high-spin heme b3associated with a CuBcenter. The protein also contains one low-spin heme b and 3 hemes c. We address here the redox properties of cbb3oxidases from three organisms, Rhodobacter sphaeroides, Vibrio cholerae and Pseudomonas stutzeri by means of electrochemical and spectroscopic techniques. We show that the redox potential of the heme b3exhibits a relatively low midpoint potential, as in related cytochrome c-dependent nitric oxide reductases. Potential implications for the coupled electron transfer and proton uptake mechanism of C-type oxidases are discussed.
Laboratoire de Bioélectrochimie et Spectroscopie, Chimie de la Matière Complexe, UMR 7140, Université de Strasbourg, 1 Rue Blaise Pascal, 67000 Strasbourg, France.
Frederic
F
Melin
Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt am Main, Germany.
Hao
H
Xie
Laboratoire de Bioélectrochimie et Spectroscopie, Chimie de la Matière Complexe, UMR 7140, Université de Strasbourg, 1 Rue Blaise Pascal, 67000 Strasbourg, France.
Thomas
T
Meyer
Department of Biochemistry, University of Illinois at Urbana Champaign, USA.
Young Ok
YO
Ahn
Department of Biochemistry, University of Illinois at Urbana Champaign, USA.
Robert B
RB
Gennis
Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt am Main, Germany.
Hartmut
H
Michel
Laboratoire de Bioélectrochimie et Spectroscopie, Chimie de la Matière Complexe, UMR 7140, Université de Strasbourg, 1 Rue Blaise Pascal, 67000 Strasbourg, France. Electronic address: hellwig@unistra.fr.
Petra
P
Hellwig
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D003578:Cytochrome-c Peroxidase / Q000378:metabolism; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006860:Hydrogen Bonding; D008024:Ligands; D008564:Membrane Potentials; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D011199:Potentiometry; D011485:Protein Binding; D011487:Protein Conformation; D011522:Protons; D044223:Pseudomonas stutzeri / Q000201:enzymology*; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D014734:Vibrio cholerae / Q000201:enzymology*
D001426:Bacterial Proteins; D008024:Ligands; D011522:Protons; D006418:Heme; D010088:Oxidoreductases; D003578:Cytochrome-c Peroxidase; C034747:nitric-oxide reductase; C414443:cbb3 oxidase; D003576:Electron Transport Complex IV; D010100:Oxygen
Heme-heme interaction; Membrane proteins; Potentiometric titrations; Protein film voltammetry; Terminal oxidases