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El ajuste del potencial de reducción en un sitio de cobre tipo 1 no compromete la reactividad de transferencia de
Sachiko Yanagisawa1, Christopher Dennison
1Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, NE2 4HH, UK.
Journal of the American Chemical Society
|November 25, 2005
Resumen
Los sitios de cobre tipo 1 son cruciales para la transferencia de electrones. La modificación de los ligandos axiales en la proteína básica del pepino sintoniza la reactividad, mostrando que una coordinación más débil mejora las tasas de transferencia de electrones.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química bioorgánica Química bioorgánica.
- Ciencia de las proteínas Ciencia de las proteínas.
Sus antecedentes:
- Los sitios de cobre tipo 1 (T1) son vitales para la transferencia biológica de electrones (ET).
- Estos sitios cuentan con conservados ligandos ecuatoriales His2Cys y ligandos axiales variables, incluyendo metionina (Met), glutamina (Gln), o la ausencia de un ligando.
- La proteína básica del pepino (CBP) es una plantacianina (PLT) con un sitio de cobre T1.
Objetivo del estudio:
- Para investigar el impacto de la variación del ligando axial en la constante de velocidad de autointercambio de electrones (ESE) y el potencial de reducción de los sitios de cobre T1.
- Comprender cómo la modulación del entorno de coordinación axial afecta la reactividad ET intrínseca de proteínas como la CBP.
Principales métodos:
- La mutagénesis dirigida al sitio se utilizó para crear las variantes Met89Gln y Met89Val de CBP.
- Las constantes de velocidad de autointercambio de electrones (ESE) (k(ese)) se midieron para evaluar la reactividad ET intrínseca.
- Se midieron los potenciales de reducción para evaluar los cambios en las propiedades electrónicas del sitio de cobre.
Principales resultados:
- La variante Met89Gln de CBP exhibió una disminución de aproximadamente 7 veces en k (((ese) en comparación con el tipo silvestre.
- La mutación Met89Val dio como resultado un aumento de 2 veces en k(ese).
- La disminución de la fuerza de interacción axial (Gln > Met > Val) aumentó la reactividad de ESE en aproximadamente un orden de magnitud y aumentó el potencial de reducción en aproximadamente 350 mV.
Conclusiones:
- El entorno de coordinación axial de los sitios de cobre T1 influye significativamente en la reactividad de ET y el potencial de reducción.
- La coordinación axial variable proporciona un mecanismo para ajustar la fuerza motriz de ET para optimizar las interacciones con los socios biológicos.
- La reactividad aumentada en los sitios de cobre T1 de tres coordenadas, como se ve en las lacasas fúngicas y Fet3p, probablemente facilita la ET intramolecular.
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