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Movimiento a gran escala del factor de alargamiento G y cambio conformacional extenso del ribosoma durante la
H Stark1, M V Rodnina, H J Wieden
1Imperial College of Science Medicine and Technology, Department of Biochemistry, London, United Kingdom.
Cell
|February 17, 2000
Resumen
El factor de alargamiento G (EF-G) impulsa el movimiento del tRNA en el ribosoma. Las estructuras cryo-EM revelan EF-G.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Biología Estructural Biología estructural.
- La bioquímica es la bioquímica.
Sus antecedentes:
- El factor de alargamiento G (EF-G) es crucial para la síntesis de proteínas bacterianas.
- EF-G facilita la translocación del ARN de transferencia (ARNt) en el ribosoma, moviéndolo desde el sitio A al sitio P.
- Comprender la dinámica estructural de EF-G durante la translocación es clave para dilucidar el mecanismo de la síntesis de proteínas.
Objetivo del estudio:
- Para visualizar los cambios estructurales del complejo EF-G-ribosoma antes y después de la translocación del ARNt.
- Investigar los estados conformacionales de EF-G durante su ciclo funcional.
- Para identificar los reordenamientos estructurales en el ribosoma inducidos por la unión y actividad de EF-G.
Principales métodos:
- Se empleó la microscopía crioectrónica (cryo-EM) para obtener reconstrucciones 3D de alta resolución.
- Se prepararon complejos de EF-G con el ribosoma en estados de pretranslocación y posttranslocación.
- El análisis estructural se centró en las interacciones entre los dominios EF-G y las subunidades ribosómicas.
Principales resultados:
- Se generaron reconstrucciones tridimensionales de complejos EF-G-ribosoma en estados de pre y posttranslocación.
- En el estado de pretranslocación, el dominio EF-G 1 interactúa con el tallo 50S L7/12 y el dominio 4 entra en contacto con la subunidad 30S cerca de la proteína S4.
- Durante la translocación, el EF-G sufre una reorientación significativa, con el dominio 4 que finalmente llega al centro de decodificación, y el ribosoma exhibe cambios estructurales sustanciales, particularmente en la subunidad 30S.
Conclusiones:
- EF-G adopta conformaciones distintas antes y después de la translocación.
- Los cambios estructurales ribosómicos, especialmente en la unión cabeza-cuerpo de la subunidad 30S, están asociados con la acción EF-G.
- Estos hallazgos sugieren un mecanismo para la translocación de tRNA mediada por EF-G.
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