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Evidencia estructural para la activación de retroalimentación por Ras.GTP del factor de intercambio de nucleótidos

S Mariana Margarit¹, Holger Sondermann, Brian E Hall

¹Department of Molecular Genetics and Microbiology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA.

|March 12, 2003

Resumen

Los receptores del factor de crecimiento activan Ras a través de son of sevenless (SOS). Ras.GTP se une a un sitio SOS distinto, estabilizando alostéricamente el sitio activo y creando un bucle de retroalimentación positiva para la regulación de Ras.

Área de la Ciencia:

Biología Molecular Biología Molecular
La señalización celular de las células.
La bioquímica es la bioquímica.

Sus antecedentes:

Los receptores del factor de crecimiento inician la señalización celular mediante la activación de Ras.
Son of sevenless (SOS) es un factor clave de intercambio de nucleótidos que activa Ras.
La activación de Ras implica el reclutamiento de SOS a la membrana celular para promover la carga de GTP.

Objetivo del estudio:

Para investigar las bases estructurales de la interacción Ras-SOS.
Aclarar el mecanismo por el cual Ras.GTP influye en la actividad de SOS.
Para identificar un potencial mecanismo de retroalimentación positiva en la señalización Ras.

Principales métodos:

Cristalografía de rayos X para determinar la estructura de Ras unido al módulo catalítico de SOS.
Ensayos bioquímicos para estudiar la interacción entre Ras.GTP y SOS en solución.
Análisis de la formación del complejo ternario y las tasas de liberación de nucleótidos.

Principales resultados:

Se identificó un sitio de unión Ras conservado en SOS, distinto del sitio activo.
Este sitio es específico para Ras.GTP.
La unión al Ras.GTP estabiliza alostéricamente el sitio activo SOS, mejorando el intercambio de nucleótidos.
Ras.GTP forma complejos ternarios con SOS (cat) y aumenta significativamente la tasa de liberación de nucleótidos de Ras.

Conclusiones:

La unión de Ras.GTP a SOS no depende únicamente del sitio catalítico.
Existe un mecanismo de retroalimentación positiva donde Ras.GTP mejora la actividad SOS.
Este mecanismo proporciona la regulación espacial y temporal de las vías de señalización Ras.

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