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Regulación a través del canal secundario--marco estructural para la sinergia ppGpp-DksA durante la transcripción
Anna Perederina1, Vladimir Svetlov, Marina N Vassylyeva
1Cellular Signaling Laboratory, Mikazuki-cho, Sayo, Hyogo 679-5148, Japan.
Cell
|August 6, 2004
Resumen
La proteína DksA es esencial para la regulación de la transcripción bacteriana por ppGpp. DksA trabaja con ppGpp para controlar la actividad de la ARN polimerasa, influyendo en la expresión génica.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Reglamento de la transcripción bacteriana.
Sus antecedentes:
- La transcripción bacteriana está modulada por la hormona guanosina tetrafosfato (ppGpp).
- ppGpp interactúa con la ARN polimerasa (RNAP) cerca de su sitio catalítico para regular la transcripción.
- El papel preciso de las proteínas reguladoras en el control mediado por ppGpp sigue siendo objeto de investigación.
Objetivo del estudio:
- Para aclarar el papel de la proteína DksA en la regulación de la transcripción bacteriana dependiente de ppGpp.
- Determinar la base estructural de la interacción de DksA-ppGpp con el RNAP.
- Investigar las consecuencias funcionales de la unión de DksA y su interacción con ppGpp.
Principales métodos:
- Cristalografía de rayos X para determinar la estructura de resolución de 2,0 Å de Escherichia coli DksA.
- Análisis bioquímicos para evaluar los efectos de DksA en el alargamiento e iniciación de transcripción.
- Mutagenesis dirigida al sitio para sustituir los residuos de aspartato conservados en DksA.
Principales resultados:
- La estructura de DksA revela un dominio globular y una región en espiral similar al factor de escisión de la transcripción GreA.
- La bobina enrollada de DksA probablemente se inserta en el canal secundario de RNAP, coordinando ppGpp y Mg2+ a través de residuos de aspartato conservados.
- DksA se une directamente a RNAP, mejora los efectos de ppGpp en la iniciación e influye en el alargamiento de transcripción de manera diferente a GreA.
- La mutación de los residuos de aspartato conservados elimina el efecto sinérgico entre DksA y ppGpp.
Conclusiones:
- DksA es un componente clave de la regulación de la transcripción dependiente de ppGpp en las bacterias.
- El canal secundario RNAP sirve como un punto de entrada común para los factores reguladores de la transcripción como DksA.
- DksA estabiliza el complejo ppGpp-RNAP a través de la interacción directa y la coordinación de ppGpp.
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