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La activación alostérica de DegS, un sensor de estrés de la proteasa PDZ
Jungsan Sohn1, Robert A Grant, Robert T Sauer
1Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Cell
|November 6, 2007
Resumen
La unión a la proteína de la membrana externa (OMP) activa la proteasa DegS a través de un mecanismo alostérico, cambiándola a un estado funcional. Este comportamiento similar a un interruptor es crucial para la transducción de señales en E. coli.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
- Biología celular Biología celular.
Sus antecedentes:
- La proteólisis intramembrana regulada (RIP) es un mecanismo clave de señalización entre los compartimentos celulares.
- En E. coli, el plegamiento de la proteína periplásmica comprometida desencadena la activación de la proteasa DegS por las proteínas de la membrana externa (OMPs).
- DegS divide RseA, un regulador de transmembrana, iniciando una cascada de señalización.
Objetivo del estudio:
- Para dilucidar el mecanismo alostérico de la activación de la proteasa DegS por parte de los PMO.
- Comprender las bases estructurales y funcionales del comportamiento similar a un interruptor de DegS.
- Para investigar la conservación de este mecanismo de activación alostérica en las proteasas relacionadas.
Principales métodos:
- Cristalografía de rayos X para determinar las estructuras de DegS.
- Análisis bioquímicos para medir la actividad de la proteasa.
- Estudios de mutagenesis para identificar residuos clave involucrados en la regulación alostérica.
Principales resultados:
- DegS funciona como una enzima alostérica, la transición de una conformación inactiva a una conformación activa en la unión de OMP.
- Los dominios PDZ no ligados de DegS son inhibidores; la unión de OMP estabiliza la conformación activa.
- Tanto la activación inducida por OMP como la unión de RseA exhiben una cooperatividad positiva, lo que permite respuestas similares a la conmutación.
- Los principales residuos alostéricos se conservan en las familias de proteasas DegP/HtrA y HtrA2/Omi.
Conclusiones:
- La unión de OMP es suficiente para activar alostericamente la proteasa DegS.
- El sistema OMP-DegS-RseA muestra propiedades similares a interruptores debido a la cooperatividad positiva.
- Un mecanismo de activación alostérica común probablemente subyace a la función de muchas de las proteasas PDZ.
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