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Estructuras cristalinas de dos complejos de proteínas Sm y sus implicaciones para el ensamblaje de los snRNP

C Kambach¹, S Walke, R Young

¹MRC Laboratory of Molecular Biology, Cambridge, England, UK.

|February 20, 1999

Resumen

Las proteínas Seven Sm forman una estructura de anillo esencial para el empalme del ARN pre-mensajero (ARNm). Las estructuras cristalinas revelan su pliegue común y la posible unión de pequeños ARN nucleares (ARN snRNA) dentro de un canal central.

Área de la Ciencia:

Biología Molecular Biología Molecular
Biología Estructural Biología estructural.
La bioquímica es la bioquímica.

Sus antecedentes:

Las pequeñas partículas de ribonucleoproteína nuclear (snRNP) son cruciales para el empalme pre-ARNm.
Las siete proteínas Sm (B/B', D1, D2, D3, E, F, G) son componentes comunes de las principales SNRNP espliceosomales.
Estas proteínas Sm se ensamblan alrededor del sitio Sm en pequeños ARN nucleares espliceosómicos (ARNEs).

Objetivo del estudio:

Para aclarar la base estructural del ensamblaje de la proteína Sm y su interacción con los snRNAs.
Comprender las características estructurales comunes y el mecanismo de ensamblaje de las siete proteínas Sm.

Principales métodos:

Se utilizó cristalografía de rayos X para determinar las estructuras de dos complejos de proteínas Sm: D3B y D1D2.2.
Análisis estructural comparativo de los complejos determinados.

Principales resultados:

Las siete proteínas Sm comparten un pliegue conservado: una hélice N-terminal seguida de una hoja beta antiparalela de cinco hebras dobladas.
Los dímeros D1D2 y D3B exhiben estructuras de núcleo muy similares, incluidas las interfaces de dímeros.
Los datos estructurales sugieren que las siete proteínas Sm pueden formar una estructura de anillo cerrado.

Conclusiones:

La estructura conservada de las proteínas Sm facilita su montaje en un anillo.
El agujero central cargado positivamente del anillo de la proteína Sm se propone como el sitio de unión para los snRNA.
Esta visión estructural proporciona una base para comprender el mecanismo de ensamblaje y función del espliceosoma.

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