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Ciclo GroEL-GroES: alternancia directa de ATP y polipéptido no nativo de anillos activos plegables

H S Rye¹, A M Roseman, S Chen

¹Howard Hughes Medical Institute, and Department of Genetics, Yale School of Medicine, New Haven, Connecticut 06510, USA.

|May 13, 1999

Resumen

La chaperonina GroEL utiliza la hidrólisis de ATP para alternar los anillos plegables de las proteínas. Este ciclo asegura un replegamiento eficiente de las proteínas al unirse a polipéptidos no nativos antes de GroES, optimizando la chaperonina.

Área de la Ciencia:

Biología molecular La biología molecular.
La bioquímica de las proteínas.
La maquinaria celular es una maquinaria celular.

Sus antecedentes:

La chaperonina GroEL de doble anillo facilita el plegamiento de proteínas dentro de su cavidad central.
Este proceso implica la unión de ATP y la cochaperonina GroES.
El mecanismo preciso del ciclo funcional de GroEL entre los estados activos de plegado sigue siendo incompletamente entendido.

Objetivo del estudio:

Para dilucidar los eventos secuenciales que rigen el ciclo funcional de la chaperonina GroEL.
Para determinar el orden de unión del sustrato y la cocaperonina en relación con la hidrólisis de ATP y los cambios en la conformación del anillo.
Para entender cómo GroEL transiciones entre sucesivos ciclos de plegamiento de proteínas.

Principales métodos:

Ensayos bioquímicos que monitorean las tasas de hidrólisis de ATP.
Análisis de la cinética de unión de polipéptido y GroES.
Observación de cambios conformacionales en los dominios apical de GroEL.

Principales resultados:

La hidrólisis de ATP en el anillo cis es un requisito previo para el polipéptido no nativo o GroES que se une al anillo trans.
Este evento de hidrólisis se combina con una reorientación de los dominios apicales del anillo trans.
La unión del polipéptido al anillo trans recién abierto estimula la disociación del complejo cis existente, facilitando la unión de GroES y el plegamiento posterior.

Conclusiones:

El ciclo funcional de GroEL implica un estricto orden secuencial de eventos: hidrólisis de ATP, unión a polipéptidos y unión a GroES.
La chaperonina alterna sus dos anillos, con cada anillo que sirve como un complejo cis activo plegable secuencialmente.
Este mecanismo alternativo permite un plegamiento eficiente de las proteínas, utilizando sólo un ciclo de siete ATPs por evento de plegamiento en presencia de proteínas no nativas.

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