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Estructura de un complejo Bag/Hsc70: evolución funcional convergente de los factores de intercambio de nucleótidos

H Sondermann¹, C Scheufler, C Schneider

¹Department of Cellular Biochemistry, Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany.

Science (New York, N.Y.)

|February 27, 2001

Resumen

Los dominios de la bolsa en los cofactores Hsp70 se unen al dominio de la ATPasa Hsp70, promoviendo la liberación del sustrato. Los estudios estructurales revelan un mecanismo de conmutación de conformación conservado para el intercambio de nucleótidos entre especies.

Área de la Ciencia:

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

Sus antecedentes:

Los dominios de la bolsa son cofactores para las chaperonas eucariotas de la proteína de choque térmico de 70 kilodaltones (Hsp70).
Las Hsp70 juegan un papel crítico en el plegamiento de las proteínas y la proteostasis celular.
La función de Hsp70 está regulada por la unión de nucleótidos y la hidrólisis.

Objetivo del estudio:

Para aclarar la base estructural de la regulación Hsp70 mediada por el dominio Bag.
Para entender el mecanismo del intercambio de nucleótidos Hsp70.
Para investigar la convergencia funcional en las interacciones del cofactor Hsp70.

Principales métodos:

Cristalografía de rayos X (resolución de 1,9 angstrom) del dominio ATPasa Hsc70 complejo con un dominio Bag.
Pruebas bioquímicas para evaluar la liberación del sustrato Hsp70.
Análisis estructural comparativo con el homólogo bacteriano Hsp70 DnaK y su cofactor GrpE.

Principales resultados:

El dominio Bag forma un haz de tres hélices que une el dominio Hsp70 ATPasa.
Esta interacción induce un cambio conformacional en Hsp70, haciéndolo incompatible con la unión de nucleótidos.
Este mecanismo se conserva funcionalmente, ya que el GrpE estructuralmente distinto también induce un interruptor similar en DnaK.

Conclusiones:

Los dominios de la bolsa actúan como factores de intercambio de nucleótidos para Hsp70s al inducir un cambio conformacional conservado.
La convergencia funcional permite que las proteínas con diferentes arquitecturas regulen la actividad de Hsp70.
Este estudio proporciona información estructural sobre la regulación de la chaperona Hsp70 y las interacciones de los cofactores.

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