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Cambios estructurales ligados al redox en la ribonucleótido reductasa
A R Offenbacher1, I R Vassiliev, M R Seyedsayamdost
1Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Journal of the American Chemical Society
|June 4, 2009
Resumen
La ribonucleótido reductasa (RNR) utiliza un radical tirosílico (Y122*) para iniciar la catálisis. Este estudio revela cambios estructurales ligados al redox en los enlaces de amida cercanos, impulsados por cambios electrostáticos en el radical.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- La ribonucleótido reductasa (RNR) es esencial para la síntesis del ADN, catalizando la producción de desoxirribonucleótidos.
- Las RNR de clase I, como la subunidad beta2 de E. coli, presentan centros de hierro y un radical libre tirosilo crítico (Y122*) para la catálisis.
- Los cambios conformacionales dependientes de redox en Y122* pueden regular la transferencia de electrones acoplados a protones.
Objetivo del estudio:
- Investigar cambios estructurales ligados al redox asociados con el radical Y122* en E. coli beta2.
- Comprender el papel del radical tirosilo en el inicio de las reacciones catalíticas.
- Para explorar el mecanismo de regulación de la transferencia de electrones acoplados a protones.
Principales métodos:
- Se utilizó la espectroscopia infrarroja de la Transformación de Fourier (FT-IR) para detectar cambios espectrales inducidos por la reacción.
- El etiquetado isotópico con (2)H(4) tirosina y (15)N tirosina ayudó en las asignaciones espectrales.
- Los espectros de diferencia se obtuvieron durante la reducción de Y122* por hidroxiurea.
Principales resultados:
- El análisis de FT-IR identificó bandas vibratorias específicas relacionadas con Y122 (1514 cm(-1)) y Y122* (1498 cm(-1)).
- Los espectros inducidos por la reacción mostraron cambios en las bandas de amida I (1661 y 1652 cm(-1)), lo que indica alteraciones estructurales.
- Estos desplazamientos de la banda de amida reflejaron los observados en un modelo de pentapeptido, lo que sugiere efectos mediados por secuencia.
Conclusiones:
- La reducción de Y122* está acoplada a perturbaciones estructurales de los enlaces amídicos cercanos.
- Estos cambios estructurales están influenciados por la secuencia de aminoácidos que rodea al radical tirosilo.
- Un mecanismo propuesto implica cambios electrostáticos ligados al redox dentro del anillo aromático del radical tirosílico que conduce a perturbaciones de enlaces amídicos.
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