Non-inhibiting perturbation of the primary energy conversion site (Qo site) in Rhodobacter capsulatus ubihydroquinone: cytochrome c oxidoreductase (cytochrome bc1 complex).
Ethanol added to Rhodobacter capsulatus chromatophore membranes containing the cytochrome bc1 complex effectively uncouples the sensitivity of the [2Fe-2S] cluster EPR spectrum to the number and redox state of ubiquinone/ubihydroquinone within the Qo site. Ethanol has no effect upon the rate of catalysis, leading to a non-inhibiting perturbation of cytochrome bc1 function. We suggest that displacement occurs by ethanol acting from the aqueous phase to successfully compete with the Qo site ubiquinones and water to hydrogen bond the N(epsilon)H atom(s) of the coordinating [2Fe-2S] cluster histidines.
Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104, USA.
R E
RE
Sharp
A
A
Palmitessa
B R
BR
Gibney
C C
CC
Moser
F
F
Daldal
P L
PL
Dutton
D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy; D014450:Electron Transport Complex III / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D016354:Rhodobacter capsulatus / Q000201:enzymology*
D000431:Ethanol; D014450:Electron Transport Complex III