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Cómo un tmRNA circularizado se mueve a través del ribosoma
Christopher D Rae1, Yuliya Gordiyenko1, V Ramakrishnan2
1Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, England, UK.
Science (New York, N.Y.)
|February 16, 2019
Resumen
El ARN mensajero de transferencia (tmRNA) y la pequeña proteína B (SmpB) rescatan los ribosomas estancados durante la traslación. Cryo-EM revela cómo este complejo se mueve a través del ribosoma para marcar las proteínas para la degradación.
Área de la Ciencia:
- Biología molecular
- Biología estructural
- La bioquímica
Sus antecedentes:
- Los ribosomas pueden detenerse en ARN mensajeros truncados o dañados (ARNm).
- La trans-traducción es un mecanismo celular conservado que rescata los ribosomas estancados.
- El ARN mensajero de transferencia (ARNm) y su proteína de unión SmpB son esenciales para la traslación.
Objetivo del estudio:
- Para aclarar los mecanismos estructurales del complejo tmRNA-SmpB-ribosoma durante la traslación.
- Para visualizar el proceso dinámico de rescate de ribosomas y etiquetado de polipéptidos en alta resolución.
Principales métodos:
- Se empleó la criomicroscopia electrónica (Cryo-EM) para determinar las estructuras complejas.
- Análisis estructural de alta resolución (3.74.4 angstroms) de los estados intermedios clave.
Principales resultados:
- Se resolvieron tres estados estructurales distintos del complejo tmRNA-SmpB-ribosoma.
- Las estructuras revelan las interacciones específicas de tmRNA y SmpB con los ribosomas estancados.
- Se visualizó el mecanismo de translocación del complejo tmRNA-SmpB a través del ribosoma.
Conclusiones:
- El tmRNA y el SmpB reconocen y se unen específicamente a los ribosomas estancados.
- El movimiento dinámico del complejo facilita el cambio de un mRNA defectuoso a tmRNA.
- Este proceso permite el marcado de los polipéptidos nacientes para la degradación, manteniendo la proteostasis celular.
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