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Dinámica ultrarrápida del ligando diatómico que se une a la nitrophorina 4
Abdelkrim Benabbas1, Xiong Ye, Minoru Kubo
1Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA.
Journal of the American Chemical Society
|February 4, 2010
Resumen
La nitroforina 4 (NP4) se une al óxido nítrico (NO) de manera diferente en sus estados ferroso y férrico. El NP4 ferroso muestra una rápida reconexión de NO, mientras que el NP4 férrico exhibe una liberación de NO dependiente del pH, crucial para su función biológica.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Dinámica de las proteínas Dinámica de las proteínas.
- La señalización del óxido nítrico.
Sus antecedentes:
- La nitroforina 4 (NP4) es una proteína hemo conocida por almacenar y liberar óxido nítrico (NO).
- Su función se basa en cambios conformacionales sensibles al pH que afectan la unión y liberación de NO.
- La proteína utiliza el estado férrico para una fuerte unión de NO a un pH bajo y su liberación a un pH alto.
Objetivo del estudio:
- Para investigar la cinética de reunión de NO y monóxido de carbono (CO) a NP4.
- Para examinar la influencia del estado de oxidación del hierro y el pH ambiental en estas cinéticas.
- Para aclarar los mecanismos subyacentes a la función de almacenamiento y liberación de NO de NP4.
Principales métodos:
- Espectroscopia cinética ultrarrápida.
- Estudios con resolución de tiempo de NO y CO que se vuelven a unir a NP4.
- Análisis de los cambios de conformación de las proteínas en función del pH.
Principales resultados:
- La recombinación del NO geminado al NP4 ferroso es rápida (~7 ps) e independiente del pH, lo que sugiere una utilidad funcional limitada del estado ferroso para la liberación de NO.
- El NP4NO férrico muestra una recombinación bifásica de NO, con una amplitud de fase más lenta que aumenta significativamente con el pH (5 a 8).
- La tasa de NO de NP4 férrico aumenta en un orden de magnitud de pH 5 a 8, correlacionándose con las conformaciones "abiertas" de las proteínas.
Conclusiones:
- El estado ferroso de NP4 no está optimizado para la liberación de NO debido a la rápida y independiente del pH reunión.
- La liberación de NO del estado férrico está modulada por cambios conformacionales dependientes del pH, específicamente la apertura del bolsillo hemo.
- La capacidad de NP4 para liberar NO está directamente relacionada con la población de estados "abiertos" y la dinámica de escape asociada, destacando su papel en la entrega de NO.
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