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Mecanismo de cierre de la cámara plegable en una chaperonina del grupo II

Junjie Zhang¹, Matthew L Baker, Gunnar F Schröder

¹Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA.

|January 22, 2010

Resumen

Las chaperoninas del grupo II usan la hidrólisis de ATP para cerrar sus tapas, facilitando el plegamiento de las proteínas. Este estudio revela los detalles atómicos de este cambio conformacional utilizando cryo-EM y modelado computacional.

Área de la Ciencia:

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

Sus antecedentes:

Las chaperoninas del grupo II son grandes máquinas de proteínas esenciales que participan en el plegamiento de las proteínas celulares.
Su función se basa en un mecanismo de tapa activado por la hidrólisis de ATP, pero la dinámica estructural subyacente era desconocida.

Objetivo del estudio:

Para dilucidar los reordenamientos estructurales y eventos moleculares que conducen al cierre de la tapa en el grupo II chaperoninas.
Proporcionar el primer modelo atómico de una chaperonina del grupo II en su conformación cerrada.

Principales métodos:

Se utilizó la criomicroscopia electrónica de partícula única (cryo-EM) para determinar las estructuras de una chaperonina del grupo II arqueal (Mm-cpn).
Se obtuvieron cuatro estructuras que representan estados libres de nucleótidos (abiertos) y inducidos por nucleótidos (cerrados).
Se empleó el modelado de redes elásticas deformables para refinar el modelo de conformación abierta.

Principales resultados:

Las estructuras cryo-EM de alta resolución revelaron los detalles atómicos de la conformación cerrada, incluida la unión de nucleótidos y la visualización de la cadena lateral.
Las estructuras abiertas y cerradas ilustran cómo la hidrólisis de ATP induce cambios conformacionales locales, alterando los contactos intersubunitarios.
Estos cambios impulsan un movimiento de balanceo que resulta en el cierre del párpado, esencial para la función de la chaperona.

Conclusiones:

Los cambios conformacionales locales desencadenados por la hidrólisis de ATP orquestan la comunicación alosterica y la señalización entre anillos necesaria para el ciclo conformacional de la chaperonina del grupo II.
El enfoque combinado de cryo-EM y modelado computacional ofrece un método poderoso para estudiar máquinas macromoleculares dinámicas en solución.

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