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Las contribuciones de la esfera externa a la estructura electrónica de las proteínas de cobre tipo cero
Kyle M Lancaster1, María-Eugenia Zaballa, Stephen Sproules
1California Institute of Technology, Pasadena, California 91125, United States. kml236@cornell.edu
Journal of the American Chemical Society
|May 9, 2012
Resumen
Los investigadores descubrieron nuevos sitios de cobre "tipo cero" en las proteínas, desafiando el canon bioinorgánico. Estos sitios, que carecen de coordinación del tiolato, exhiben estructuras electrónicas únicas y propiedades de transferencia de electrones.
Área de la Ciencia:
- Química bioorgánica y bioorgánica.
- La biofísica es la biofísica.
- La ingeniería de proteínas es la ingeniería de proteínas.
Sus antecedentes:
- El canon bioinorgánico establecido postula que la coordinación del tiolato en el sitio activo es esencial para la rápida transferencia de electrones (ET) en las proteínas de cobre tipo 1.
- Los hallazgos recientes indican que los sitios de ET de cobre pueden ser diseñados sin ligadura de tiolato, denominados sitios de "tipo cero".
Objetivo del estudio:
- Para investigar las propiedades estructurales y electrónicas de los sitios de cobre tipo cero en las variantes de Pseudomonas aeruginosa azurin.
- Para comparar las estructuras electrónicas de los sitios de tipo cero con los centros de cobre de tipo salvaje (tipo 1) y tipo 2.
Principales métodos:
- Espectroscopia de resonancia paramagnética de electrones de frecuencia múltiple (EPR), dicroísmo magnético circular (MCD) y resonancia magnética nuclear (RMN).
- Cálculos de la teoría funcional de la densidad (DFT) y la interacción de configuración orientada a la espectroscopia (SORCI).
- Simulaciones de mecánica cuántica y mecánica molecular (QM/MM).
Principales resultados:
- Los centros de cobre tipo cero en las variantes de Pseudomonas aeruginosa azurin exhiben campos de ligandos prácticamente idénticos a los centros tipo 1 de tipo salvaje.
- Se observó una mayor covalencia del donante O y una reducción de la covalencia del donante N en los centros de tipo cero en comparación con las proteínas de tipo 1 y tipo 2.
- Las estructuras electrónicas de los sitios de tipo cero y tipo 2 están fuertemente influenciadas por la orientación y coordinación del ligando carboxilato, modulado por enlaces de hidrógeno de la esfera externa.
Conclusiones:
- Los sitios de cobre de tipo cero representan una alternativa viable a los sitios tradicionales de tipo 1 para modular las propiedades de transferencia de electrones.
- La coordinación y orientación de los ligandos carboxilados, influenciados por la unión de hidrógeno, son determinantes críticos de la estructura electrónica en los centros de cobre no tiolado.
- Este estudio amplía la comprensión de los sitios activos de la proteína de cobre y ofrece nuevas vías para la ingeniería de proteínas.
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