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Mecanismo atómico de transición conformacional a gran escala en un exportador ABC heterodímero

Hendrik Göddeke¹, M Hadi Timachi², Cedric A J Hutter³

¹Theoretical Chemistry, Faculty of Chemistry and Biochemistry , Ruhr-University Bochum , 44780 Bochum , Germany.

Journal of the American Chemical Society

|March 17, 2018

Resumen

Este estudio revela el mecanismo atómico del transportador de casete de unión al ATP (ABC) TM287/288. Muestra cómo la unión de ATP impulsa cambios conformacionales, moviendo el transportador de estados orientados hacia adentro a estados orientados hacia afuera a través de un intermedio oculto.

Área de la Ciencia:

Biología estructural
La bioquímica
Biofísica molecular

Sus antecedentes:

Los transportadores de cassette de unión de ATP (ABC) utilizan la unión de ATP y la hidrólisis para la translocación del sustrato.
El acoplamiento dinámico entre los dominios de unión de nucleótidos (NBD) y los dominios transmembrana (TMD) sigue siendo poco conocido.
La comprensión de estas dinámicas es crucial para elucidar el mecanismo del transporte de la membrana.

Objetivo del estudio:

Para aclarar el mecanismo a nivel atómico de las transiciones conformacionales en el exportador ABC TM287/288.
Para caracterizar los estados ocluidos y orientados hacia el exterior a resolución atómica.
Investigar el acoplamiento entre los movimientos del NBD y del TMD durante el ciclo de transporte.

Principales métodos:

Simulaciones de dinámica molecular de todos los átomos.
Espectroscopia de resonancia paramagnética de electrones (EPR).
Simulaciones realizadas en un entorno de membrana/agua explícito durante varios microsegundos.

Principales resultados:

TM287/288 transiciones de estados orientados hacia adentro (IF) a estados orientados hacia afuera (OF) a través de un intermediario ocluido (Occ) en la unión de ATP.
La unión de ATP induce el apretamiento del dímero NBD y el cierre de la puerta TMD intracelular, formando el estado Occ.
La posterior apertura de la puerta TMD extracelular conduce al estado OF, con puertas que nunca se abren simultáneamente.

Conclusiones:

Se propone un mecanismo atómico detallado para el ciclo conformacional TM287/288.
El acoplamiento NBD-TMD se logra a través de cambios de conformación coordinados de dominio e intra-TMD.
El estudio proporciona información a nivel atómico sobre el ciclo de trabajo funcional de los exportadores de ABC heterodiméricos.

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