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Una mutación remota afecta la transferencia de hidruro al interrumpir los movimientos concertados de proteínas en la
Zhen Wang1, Thelma Abeysinghe, Janet S Finer-Moore
1Department of Chemistry, University of Iowa, Iowa City, Iowa 52242-1727, USA.
Journal of the American Chemical Society
|October 5, 2012
Resumen
La flexibilidad de las proteínas es clave para la función de las enzimas. Una mutación en la timidilato sintasa (TSasa) interrumpió los movimientos de las proteínas, reduciendo la actividad al alterar la preorganización del sitio activo para la transferencia de hidruro.
Área de la Ciencia:
- Enzimología y dinámica de proteínas.
- Mecanismos bioquímicos y cinética.
Sus antecedentes:
- La flexibilidad y la dinámica de las proteínas son cada vez más reconocidas como cruciales para la catálisis enzimática.
- La timidilato sintasa (TSasa) cataliza las reacciones esenciales de transferencia de hidruro.
Objetivo del estudio:
- Para investigar el papel de los movimientos de proteínas en la reacción de transferencia de hidruro catalizado por Escherichia coli timidilato sintasa (TSase).
- Para analizar el impacto de la mutación Y209W en la actividad y el mecanismo de la TSasa.
Principales métodos:
- Análisis comparativo de las estructuras cristalinas del tipo salvaje y la TSasa mutante Y209W en complejo con ligandos.
- Examen de factores B anisotrópicos para evaluar las vibraciones de los residuos de proteínas.
- Estudios cinéticos, incluida la entalpía de activación y la dependencia de la temperatura del efecto isotópico cinético intrínseco (KIE).
Principales resultados:
- La mutación Y209W, localizada a distancia del sitio activo, redujo significativamente la actividad de la TSasa.
- El análisis estructural reveló vibraciones atómicas correlacionadas interrumpidas en el mutante, indicadas por factores B anisotrópicos.
- La mutación condujo a una mayor entalpía de activación para la transferencia de hidruro, pero tuvo un efecto mínimo en la dependencia de la temperatura de la KIE.
Conclusiones:
- La mutación Y209W interrumpe los movimientos esenciales de las proteínas que preorganizan el entorno para la transferencia de hidruro.
- Estos hallazgos resaltan la importancia de la dinámica concertada de las proteínas en múltiples escalas de tiempo para una catálisis enzimática eficiente.
- El estudio proporciona información sobre cómo la flexibilidad de las proteínas influye en la activación de enlaces químicos en las enzimas.
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