Nucleotide binding affinities of the intact proton-translocating transhydrogenase from Escherichia coli.
Biochim Biophys Acta
; 1708(3): 404-10, 2005 Jul 15.
Article
en En
| MEDLINE
| ID: mdl-15935988
ABSTRACT
Transhydrogenase (E.C. 1.6.1.1) couples the redox reaction between NAD(H) and NADP(H) to the transport of protons across a membrane. The enzyme is composed of three components. The dI and dIII components, which house the binding site for NAD(H) and NADP(H), respectively, are peripheral to the membrane, and dII spans the membrane. We have estimated dissociation constants (K(d) values) for NADPH (0.87 microM), NADP(+) (16 microM), NADH (50 microM), and NAD(+) (100-500 microM) for intact, detergent-dispersed transhydrogenase from Escherichia coli using micro-calorimetry. This is the first complete set of dissociation constants of the physiological nucleotides for any intact transhydrogenase. The K(d) values for NAD(+) and NADH are similar to those previously reported with isolated dI, but the K(d) values for NADP(+) and NADPH are much larger than those previously reported with isolated dIII. There is negative co-operativity between the binding sites of the intact, detergent-dispersed transhydrogenase when both nucleotides are reduced or both are oxidized.
Buscar en Google
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Escherichia coli
/
NADP Transhidrogenasas
/
Nucleótidos
Idioma:
En
Revista:
Biochim Biophys Acta
Año:
2005
Tipo del documento:
Article
País de afiliación:
Francia