Role of a bound ubiquinone on reactions of the Escherichia coli cytochrome bo with ubiquinol and dioxygen.
FEBS Lett
; 457(2): 223-6, 1999 Aug 27.
Article
en En
| MEDLINE
| ID: mdl-10471783
ABSTRACT
To probe the functional role of a bound ubiquinone-8 in cytochrome bo-type ubiquinol oxidase from Escherichia coli, we examined reactions with ubiquinol-1 and dioxygen. Stopped-flow studies showed that anaerobic reduction of the wild-type and the bound ubiquinone-free (DeltaUbiA) enzymes with ubiquinol-1 immediately takes place with four kinetic phases. Replacement of the bound ubiquinone with 2,6-dibromo-4-cyanophenol (PC32) suppressed the anaerobic reduction of the hemes with ubiquinol-1 by eliminating the fast phase. Flow-flash studies in the reaction of the fully reduced enzyme with dioxygen showed that the heme b-to-heme o electron transfer occurs with a rate constant of approximately 1x10(4) s(-1) in all three preparations. These results support our previous proposal that the bound ubiquinone is involved in facile oxidation of substrates in subunit II and subsequent intramolecular electron transfer to low-spin heme b in subunit I.
Buscar en Google
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Oxígeno
/
Ubiquinona
/
Grupo Citocromo b
/
Citocromos
/
Proteínas de Escherichia coli
/
Escherichia coli
Idioma:
En
Revista:
FEBS Lett
Año:
1999
Tipo del documento:
Article