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Estructura cristalina de la ARN polimerasa bacteriana unida a una proteína inhibidora de la transcripción

Shunsuke Tagami¹, Shun-Ichi Sekine, Thirumananseri Kumarevel

¹Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

|December 3, 2010

Resumen

El homólogo del factor gris 1 (Gfh1) inhibe la transcripción al bloquear la entrada del nucleótido trifosfato en la ARN polimerasa (ARNP). Esta unión bloquea el RNAP en un estado estructural alternativo, evitando la expresión génica.

Área de la Ciencia:

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

Sus antecedentes:

La ARN polimerasa dependiente del ADN (RNAP) es crucial para la expresión génica y está regulada por factores de transcripción.
El homólogo del factor gre 1 (Gfh1) del género Thermus inhibe la transcripción al unirse al RNAP.
El mecanismo estructural de la inhibición de la transcripción mediada por Gfh1 era previamente desconocido.

Objetivo del estudio:

Para aclarar la base estructural de la inhibición de la transcripción por Gfh1.1.
Para determinar la estructura del complejo RNAP-Gfh1 de Thermus thermophilus.

Principales métodos:

Cristalografía de rayos X con rayos X.
Análisis estructural del complejo RNAP-Gfh1

Principales resultados:

El dominio en espiral en espiral amino-terminal de Gfh1 obstruye el canal de entrada de nucleótido trifosfato (NTP) en el RNAP.
Gfh1 se posiciona en el sitio de unión de fosfato β-γ de la NTP.
El RNAP adopta un "estado enrejado" con canales expandidos y una hélice de puente torcida, inducida por la unión Gfh1.

Conclusiones:

Gfh1 inhibe la transcripción mediante la prevención de la unión a NTP y la estabilización de una conformación RNAP alternativa.
El "estado trenzado" también puede influir en la translocación de RNAP y la terminación de la transcripción.

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