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Estructuras y mecanismo de activación del sistema antifágico de Gabija
Jing Li1,2,3,4, Rui Cheng5, Zhiming Wang1,2,3,4
1Department of Cardiovascular Surgery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, China.
Nature
|March 12, 2024
Resumen
El sistema de defensa procariótico de Gabija utiliza GajA y GajB para luchar contra los fagos. El agotamiento de ATP activa GajA para dividir el ADN, lo que lleva a la muerte celular y la defensa de los fagos.
Área de la Ciencia:
- Biología molecular
- Microbiología
- Biología estructural
Sus antecedentes:
- Los procariotas poseen sistemas inmunológicos innatos para defenderse de las infecciones por bacteriófagos.
- El sistema Gabija, que comprende GajA y GajB, es un mecanismo de defensa procariótico generalizado.
- GajA actúa como una endonucleasa de ADN, típicamente inhibida por el ATP.
Objetivo del estudio:
- Para aclarar el mecanismo de activación del sistema Gabija contra la infección de los fagos.
- Determinar la base estructural de la función del sistema Gabija a través de la criomicroscopia electrónica.
Principales métodos:
- Para visualizar las estructuras del sistema de Gabija se empleó la criomicroscopia electrónica (Cryo-EM).
- Se analizaron cinco estados distintos de los componentes GajA y GajB: apo, ligado al ADN, ligado al ATP y complejos GajA-GajB con ATP y Mg2+.
Principales resultados:
- GajA es un tetrámero con un dominio ATPasa central y un dominio Toprim periférico.
- La unión de ATP estabiliza GajA en una conformación cerrada, inhibiendo la unión al ADN.
- El agotamiento de ATP por los fagos desencadena la apertura del dominio de Toprim para la unión y la escisión del ADN.
- GajB, al acoplarse a GajA, es activado por el ADN escindido, iniciando la muerte celular.
Conclusiones:
- El estudio revela el mecanismo paso a paso de la activación del sistema Gabija.
- Las percepciones estructurales explican cómo los niveles de ATP regulan la actividad de GajA en la defensa de los fagos.
- El sistema Gabija representa una estrategia de defensa procariota crucial contra los invasores virales.
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