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Regulación dinámica de la migración de ligandos por un interruptor molecular que abre la puerta en la hemoglobina
Axel Bidon-Chanal1, Marcelo A Martí, Darío A Estrin
1Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, Avenida Diagonal 643, 08028, Barcelona, Spain.
Journal of the American Chemical Society
|May 10, 2007
Resumen
La Mycobacterium tuberculosis utiliza truncada la hemoglobina-N para neutralizar el óxido nítrico (NO) dañino. La dinámica molecular revela un interruptor TyrB10-GlnE11 que controla la entrada de NO en la cavidad hemo, crucial para la supervivencia de las bacterias.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
- Microbiología Microbiología.
Sus antecedentes:
- La Mycobacterium tuberculosis emplea la hemoglobina truncada-N (HbN) como una defensa contra el óxido nítrico (NO) derivado de los macrófagos.
- El HbN desintoxica el NO convirtiéndolo en nitrato, un proceso limitado por la cinética de difusión de ligandos.
- Comprender la regulación de la difusión de ligandos es fundamental para elucidar los mecanismos de supervivencia bacteriana.
Objetivo del estudio:
- Investigar el mecanismo molecular que regula la difusión de ligandos en la truncada hemoglobina-N.
- Para determinar el papel de los residuos específicos de aminoácidos en el control del acceso de NO a la cavidad del hemo.
- Para dilucidar cómo la unión de oxígeno influye en la difusión de NO y la actividad enzimática.
Principales métodos:
- Se emplearon simulaciones de dinámica molecular extendida.
- El análisis se centró en el papel de los residuos que ayudan a la unión de O2 al grupo hemo.
- Se examinaron los cambios de conformación en la unión de O2 y en formas mutantes.
Principales resultados:
- El par TyrB10-GlnE11 actúa como un interruptor molecular, regulando dinámicamente el acceso de NO a la cavidad del hemo.
- La unión de O2 induce cambios conformacionales en TyrB10-GlnE11, favoreciendo la apertura de la puerta PheE15.
- Las mutaciones en GlnE11 y TyrB10 alteran significativamente la dinámica conformacional y reducen la actividad enzimática.
Conclusiones:
- Existe un mecanismo molecular para asegurar el acceso de NO a la cavidad hemo en la forma oxigenada de HbN.
- Este mecanismo es vital para la supervivencia de Mycobacterium tuberculosis bajo condiciones de estrés inducidas por el huésped.
- El par TyrB10-GlnE11 es esencial para la eficiencia catalítica del HbN en la desintoxicación del NO.
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