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Principios de la unión de ligandos dentro de una cavidad completamente enterrada en HIF2alpha PAS-B
Jason Key1, Thomas H Scheuermann, Peter C Anderson
1Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8816, USA.
Journal of the American Chemical Society
|December 3, 2009
Resumen
Las moléculas pequeñas se unen rápidamente al dominio HIF2alfa PAS-B, a pesar de su estructura cerrada. Esta unión implica un estado de transición desordenado, lo que sugiere una proteína dinámica que facilita la entrada del ligando.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
- Biología Estructural Biología estructural.
Sus antecedentes:
- Los factores inducibles a la hipoxia (HIF) regulan la respuesta celular a la falta de oxígeno y están implicados en la progresión del cáncer.
- El dominio HIF2alpha PAS-B posee una cavidad única y preexistente capaz de unir moléculas pequeñas artificiales.
- Estos ligandos modulan alostéricamente la formación de heterodímeros HIF, impactando las vías relacionadas con el cáncer.
Objetivo del estudio:
- Para dilucidar los mecanismos estructurales y termodinámicos de la unión de ligando artificial al dominio HIF2alfa PAS-B.
- Investigar la dinámica del dominio HIF2alfa PAS-B y su interacción con los inhibidores de moléculas pequeñas.
- Para entender cómo los ligandos acceden al bolsillo de unión aparentemente inaccesible.
Principales métodos:
- Calorimetría de titulación isotérmica (ITC) para el análisis termodinámico.
- Espectroscopia de intercambio de RMN (NXS) para sondear la dinámica de las proteínas.
- Cristalografía de rayos X para determinar estructuras de alta resolución.
- Simulaciones de dinámica molecular (DM) para modelar cambios de conformación de proteínas y vías de ligando.
Principales resultados:
- La unión de ligandos a HIF2alfa PAS-B se caracteriza por tasas de asociación rápidas, independientemente de los cambios conformacionales lentos.
- El análisis termodinámico revela contribuciones entálpicas y entrópicas compensadoras, indicativas de un estado de transición de unión-competencia desordenado.
- La cristalografía de rayos X y la espectroscopia de RMN muestran una conformación predominantemente cerrada del bolsillo de unión.
- Las simulaciones de MD demuestran la flexibilidad conformacional de la proteína, con interconversión entre estados abiertos y cerrados, e identifican las vías de entrada de ligandos.
Conclusiones:
- El dominio HIF2alfa PAS-B exhibe una flexibilidad inherente, permitiendo un rápido acceso al ligando a pesar de una estructura de estado cerrado.
- La unión de ligandos es facilitada por un estado de transición con un mayor trastorno estructural, lo que permite una interacción eficiente.
- Comprender estas dinámicas es crucial para diseñar inhibidores de moléculas pequeñas eficaces dirigidos a las vías HIF en la terapia del cáncer.
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