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Dinámica de la transferencia de protones en el bacteriorhodopsin
1Center for Molecular Modeling, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892, USA. leeys@mail.nih.gov
Journal of the American Chemical Society
|February 20, 2004
Resumen
La transferencia de protones en la bacteriorhodopsina se produce a través de un canal de agua, incluso a través de regiones hidrofóbicas. Este evento rápido y concertado facilita el movimiento de protones desde Asp96 a la base de Schiff.
Área de la Ciencia:
- La biofísica es la biofísica.
- Biología Estructural Biología estructural.
- Química computacional es la química computacional.
Sus antecedentes:
- La bacteriorhodopsina facilita el transporte de protones a través de las membranas.
- La transferencia de protones es crucial para la transducción de energía.
- El mecanismo de la transferencia de protones a través de los canales hidrofóbicos sigue sin estar claro.
Objetivo del estudio:
- Para investigar el mecanismo de transferencia de protones a través de un canal parcialmente hidrofóbico en el bacteriorhodopsin.
- Para dilucidar el papel de las moléculas de agua en la facilitación de la transferencia de protones.
- Para entender la dinámica de la transferencia de protones de Asp96 a la base de Schiff.
Principales métodos:
- Se construyó un modelo de mecánica cuántica / mecánica molecular (QM / MM) utilizando la estructura cristalina mutante de la bacteriorhodopsina E204Q.
- Se realizaron simulaciones de dinámica ab initio utilizando la metodología CHARMM/GAMESS.
- Los residuos clave (Asp96, Asp85, Thr89) y el cromóforo retiniano fueron tratados mecánicamente cuántico.
Principales resultados:
- Se forma un canal de agua entre Asp96 y la base de Schiff en el estado de M.
- La transferencia de protones se produce como un evento rápido (<1 ps), concertado una vez que se establece una cadena de agua.
- La transferencia de protones es independiente del estado de protonación de Asp85.
- La transferencia se inicia mediante la donación de protones de Asp96 a la molécula de agua más cercana.
Conclusiones:
- Las moléculas de agua son esenciales para mediar la transferencia de protones a través de las regiones hidrofóbicas de la bacteriorhodopsina.
- Un mecanismo concertado y rápido de transferencia de protones es facilitado por una cadena de agua estructurada.
- Este estudio proporciona información sobre la dinámica de la transferencia de protones en los sistemas biológicos.
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