title: Thermodynamic and spectroscopic characteristics of the cytochrome bc1 complex. Role of quinone in the behavior of cytochrome b562.
abstract: Cytochrome b562 does not behave as a single independent thermodynamic component in preparations of purified quinol cytochrome c reductase. This effect is much more pronounced in quinone sufficient preparations; in such preparations, the epr spectrum of the cytochrome is Eh sensitive, with a peak shift from g = 3.42 to 3.48 occurring as the potential is lowered from 100 mV to 0 mV. The peak shift is dependent on the presence of quinone and can be restored to quinone-depleted preparations by supplementation with ubiquinol 2 if phospholipid depletion is not too severe. The results suggest that cytochrome b562 is strongly interacting with the Qc quinone binding site.
authors.affiliation: Department of Biology, Rensselaer Polytechnic Institute, Troy, New York 12180-3590.
authors.forename: J C
authors.initials: JC
authors.lastname: Salerno
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: M P
authors.initials: MP
authors.lastname: Osgood
authors.forename: C H
authors.initials: CH
authors.lastname: Kim
authors.forename: T E
authors.initials: TE
authors.lastname: King
mesh_terms: D001665:Binding Sites; D003573:Cytochrome b Group / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D014450:Electron Transport Complex III / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007700:Kinetics; D009245:NADH Dehydrogenase / Q000378:metabolism; D011199:Potentiometry; D011485:Protein Binding; D011809:Quinones / Q000378:metabolism*; D013053:Spectrophotometry / Q000379:methods; D013816:Thermodynamics
chemical_list: D003573:Cytochrome b Group; D029968:Escherichia coli Proteins; D011809:Quinones; C017850:cytochrome b562, E coli; D009245:NADH Dehydrogenase; D014450:Electron Transport Complex III