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Estructura cryo-EM del complejo de defensa antimofágico supramolecular RADAR

Brianna Duncan-Lowey¹, Nitzan Tal², Alex G Johnson¹

¹Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA; Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.

|February 10, 2023

Resumen

El sistema de defensa bacteriana RADAR utiliza las proteínas RdrA y RdrB para convertir ATP en ITP, limitando la replicación de los fagos. Esta modificación de nucleótidos es clave para RADAR

Área de la Ciencia:

Inmunidad bacteriana y mecanismos de defensa
Biología estructural y microscopía criolectrónica
Mecanismos moleculares del metabolismo de los nucleótidos

Sus antecedentes:

RADAR (Reconocimiento de la actividad asociada al ADN) es un sistema de defensa bacteriana.
Anteriormente se sabía que se defendía contra los bacteriófagos modificando el ARN mensajero.
La estructura molecular detallada y el mecanismo permanecieron en gran parte desconocidos.

Objetivo del estudio:

Determinar las estructuras de la criomicroscopia electrónica (cryo-EM) del complejo de defensa RADAR.
Para aclarar el mecanismo molecular por el cual RADAR confiere inmunidad anti-fago.
Para identificar la modificación específica del nucleótido involucrado en la defensa.

Principales métodos:

Microscopía cryoelectrónica (cryo-EM) para resolver las estructuras de alta resolución del complejo RADAR.
Ensayos bioquímicos para comprobar la actividad enzimática in vitro.
Experimentos in vivo para observar la acumulación de nucleótidos durante la infección del fago.

Principales resultados:

Las estructuras cryo-EM revelaron RdrA como una ATPasa AAA+ heptámica y RdrB como un complejo dodecamérico con sitios activos de aminasa.
RdrA y RdrB forman un conjunto grande (hasta 10 MDa) con RdrA colocado sobre el sitio activo de RdrB.
RdrB cataliza la conversión de ATP a trifosfato de inosina (ITP) in vitro y conduce a la acumulación de ITP durante la infección de los fagos, inhibiendo su replicación.

Conclusiones:

La inmunidad RADAR está determinada por la desaminación de mononucleótidos de ATP, no por la edición de ARN.
El estudio revela un nuevo mecanismo de defensa antifágico a través del ensamblaje supramolecular de una máquina modificadora de nucleótidos.
Este trabajo redefine la función del sistema RADAR en la defensa bacteriana.

Palabras clave:

Desaminasa de la adenosina inmunidad antifágico el fago

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