Influence of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline modification on proton translocation and membrane potential of reconstituted cytochrome-c oxidase support "proton slippage".
J Biol Chem
; 266(13): 8097-101, 1991 May 05.
Article
em En
| MEDLINE
| ID: mdl-1850736
ABSTRACT
Bovine heart cytochrome-c oxidase was reconstituted in liposomes and modified with N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). EEDQ reacted mainly with subunits II and III and to a lower extent with subunit I, as shown by difference labeling with [14C]dicyclohexylcarbodiimide. EEDQ treatment of cytochrome-c oxidase vesicles influenced ferrocytochrome c-induced proton pumping by reducing maximally the H+/e- stoichiometry from 0.84 (control) to 0.24, but had only small effects on respiration, respiratory control ratio, and proton conductivity of the proteoliposomes. By titrating the reaction rate of the control and the modified cytochrome-c oxidase vesicles versus the membrane potential, as measured with a Ph3MeP+ electrode, saturation curves are obtained, which in both cases approach 225 mV. The ratios of electron transport rates of the two proton pumps at various membrane potentials decrease between 160 and 225 mV from about 2.2 to 1, indicating that the nonlinear flow/force relationship of these proton pumps is at least partly due to "slippage" of proton pumping.
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Base de dados:
MEDLINE
Assunto principal:
Quinolinas
/
Complexo IV da Cadeia de Transporte de Elétrons
Limite:
Animals
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
1991
Tipo de documento:
Article
País de afiliação:
Alemanha