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El origen de la división en el estado fotoproducto inicial de MbCOCO
Karin Nienhaus1, John S Olson, Stefan Franzen
1University of Ulm, Department of Biophysics, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
Journal of the American Chemical Society
|January 6, 2005
Resumen
La mioglobina es la misma que la mioglobina.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Las cavidades internas de la mioglobina (Mb) actúan como sitios de acoplamiento para los ligandos de monóxido de carbono (CO).
- Los ligandos de CO en la mioglobina exhiben bandas de estiramiento infrarrojas (IR) características debido a las interacciones del campo eléctrico local.
- Un doble de bandas de IR (B1 y B2) indica dos orientaciones para el CO en el sitio de acoplamiento primario.
Objetivo del estudio:
- Para asignar bandas IR específicas (B1 y B2) a las orientaciones de CO dentro de la mioglobina.
- Para investigar la influencia de las mutaciones de His64 y Val68 en las orientaciones de los ligandos de CO.
- Para aclarar el papel del entorno electrostático en las orientaciones de enlace de CO.
Principales métodos:
- Se empleó la espectroscopia de infrarrojos con transformación de Fourier (FTIR) para analizar las bandas de estiramiento de IR.
- Los cálculos de la teoría funcional de la densidad (DFT) se utilizaron para interpretar los efectos electrostáticos.
- Las variantes mutantes de mioglobina (H64L, V68F, H64L-V68F) se estudiaron junto con el tipo salvaje MbCO.
Principales resultados:
- La cadena lateral de imidazol de His64 se identifica como el principal contribuyente a la división de Stark.
- La banda de alta frecuencia B1 está asignada al CO orientado con carbono hacia el hierro hemo y el protón Nepsilon-H de His64.
- La banda de baja frecuencia B2 corresponde a la orientación CO opuesta.
Conclusiones:
- His64 juega un papel crucial en la determinación de la orientación del CO y las propiedades espectrales IR en la mioglobina.
- Los ligandos de CO se reorientan dinámicamente del estado menos estable de B2 al estado más estable de B1 a bajas temperaturas antes de volver a unirse.
- La comprensión de estas orientaciones proporciona información sobre las interacciones ligando-proteína y la dinámica en las proteínas hemo.
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