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La unión alostérica de nucleósidos trifosfatos a la ARN polimerasa regula el alargamiento de la transcripción

J E Foster¹, S F Holmes, D A Erie

¹Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA.

|August 21, 2001

Resumen

Los investigadores descubrieron un nuevo sitio de unión alostérico en la E. coli ARN polimerasa. La unión de nucleótidos templados a este sitio activa la enzima, aumentando la tasa de alargamiento de la transcripción.

Área de la Ciencia:

Biología Molecular Biología Molecular
La bioquímica es la bioquímica.
La cinética de las enzimas.

Sus antecedentes:

La regulación de la transcripción involucra estados conformacionales de la ARN polimerasa.
Los factores que controlan estos estados no se comprenden completamente.
Comprender la dinámica de la ARN polimerasa es crucial para el control de la expresión génica.

Objetivo del estudio:

Para investigar los factores que controlan los estados conformacionales de la ARN polimerasa.
Para aclarar el mecanismo de regulación de la incorporación de nucleótidos.
Para identificar la regulación alostérica en la función de la ARN polimerasa.

Principales métodos:

Cinética del estado transitorio para estudiar la incorporación de un solo nucleótido.
Análisis de la cinética enzimática de la ARN polimerasa de E. coli.
Caracterización de los sitios de unión de nucleótidos.

Principales resultados:

La ARN polimerasa de E. coli posee un sitio de unión alostérico distinto del sitio catalítico.
La unión de trifosfatos nucleósidos templados (NTP) al sitio alostérico aumenta las tasas de incorporación de nucleótidos.
Las NTP no templadas no se unen ni afectan el sitio alostérico.
La ARN polimerasa existe en estados catalíticos lentos (no activados) y rápidos (activados).
La unión de NTPs plantilladas al sitio alostérico induce la transición del estado no activado al estado activado.

Conclusiones:

Un sitio alostérico en la polimerasa de ARN de E. coli regula la elongación de la transcripción.
La unión de NTP con plantilla a este sitio activa la enzima para una incorporación más rápida de nucleótidos.
Este mecanismo proporciona información sobre el control de la dinámica conformacional de la ARN polimerasa durante la transcripción.

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