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Residuos de tirosina redox-activos: el papel del enlace péptido en la transferencia de electrones
Idelisa Pujols-Ayala1, Colette A Sacksteder, Bridgette A Barry
1Department of Biochemistry, Biophysics, and Molecular Biology, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Avenue, St. Paul, MN 55108, USA.
Journal of the American Chemical Society
|June 19, 2003
Resumen
La transferencia de electrones del fotosistema II implica la tirosina redox-activa Z. La oxidación perturba el enlace péptido, lo que sugiere la deslocalización del espín en la columna vertebral del péptido durante la fotosíntesis.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Investigación de fotosíntesis Investigación de fotosíntesis.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- El fotosistema II (PSII) es crucial para la oxidación del agua impulsada por la luz y la reducción de la plastoquinona.
- La tirosina Z redox-activa actúa como un conducto de electrones desde el donante de clorofila hasta el clúster de manganeso en PSII.
Objetivo del estudio:
- Investigar los cambios estructurales en el fotosistema II tras la oxidación de la tirosina Z.
- Para determinar el papel del enlace peptídico en las reacciones de transferencia de electrones dentro de PSII.
Principales métodos:
- Utilizó la espectroscopia infrarroja de la Transformación de Fourier (FT-IR) para analizar muestras de PSII.
- Se emplea tirosina etiquetada isotópicamente (etiquetada en anillo 2H4) para identificar modos de vibración específicos.
- Se realizó un análisis comparativo con compuestos modelo (tirosinato y su isotopómero).
Principales resultados:
- La oxidación de la tirosina Z en PSII indujo perturbaciones significativas en el enlace peptídico.
- Los espectros de FT-IR revelaron bandas vibratorias atribuibles a los modos imida y amida, lo que indica cambios estructurales.
- Las perturbaciones observadas son consistentes con la deslocalización de espín en el enlace péptido, respaldada por cálculos funcionales de densidad.
Conclusiones:
- El enlace péptido en PSII está involucrado en reacciones de transferencia de electrones mediadas por el radical tirosilo.
- La deslocalización del espín en el enlace péptido influye en la ruta de migración del agujero de electrones en PSII.
- Estos hallazgos ofrecen información sobre los intrincados mecanismos de la fotosíntesis y las cadenas de transporte de electrones.
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