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Emine Yikilmaz1, Jason Porta, Laurie E Grove
1Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA.
Journal of the American Chemical Society
|July 14, 2007
Resumen
La actividad de la enzima superóxido dismutasa (SOD) está sintonizada por sus iones metálicos.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- Ingeniería de proteínas Ingeniería de proteínas.
Sus antecedentes:
- Las enzimas superóxido dismutasa (SOD) catalizan la desproporción de los radicales superóxido.
- El potencial de reducción del punto medio (Em) del ion metálico del sitio activo es crucial para la actividad catalítica de SOD.
- E. coli SOD que contiene Fe (FeSOD) utiliza una pareja redox Fe3 + / Fe2 +, influenciada por los eventos de protonación.
Objetivo del estudio:
- Investigar la base estructural y electrónica de la elevación de Em en las mutaciones FeSOD de E. coli.
- Para entender cómo las mutaciones en un residuo de Gln conservado afectan a las propiedades redox de FeSOD.
- Para dilucidar el papel de la transferencia de protones acoplados a redox en la modulación de la actividad enzimática.
Principales métodos:
- Mutagénesis dirigida al sitio (Gln a His, Gln a Glu).
- Técnicas espectroscópicas: EPR, MCD y RMN.
- Cristalografía de rayos X (resolución de 1,1 Å).
- Cálculos de la Teoría Funcional de la Densidad (DFT).
Principales resultados:
- Las mutaciones Q69H y Q69E elevaron significativamente el Em de FeSOD.
- Los datos espectroscópicos indicaron estructuras electrónicas del sitio activo similares a las WT para ambos mutantes.
- Q69E-FeSOD mostró dinámicas alteradas de transferencia de protones y enlaces de hidrógeno en el estado reducido.
- La estructura cristalina de Q69E-Fe2+SOD reveló una fuerte aceptación de enlaces H por Glu69.
Conclusiones:
- La matriz proteica influye significativamente en el Em de FeSOD a través de la transferencia de protones acoplados a redox.
- El enlace de hidrógeno alterado y la transferencia de protones en Q69E-FeSOD explican el aumento de Em.
- Estos hallazgos apoyan la hipótesis del ajuste redox mediado por proteínas en las metalloenzimas.
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