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La estructura del sitio activo de una β-hidroxilasa en la biosíntesis de antibióticos
Van V Vu1, Thomas M Makris, John D Lipscomb
1Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Journal of the American Chemical Society
|April 22, 2011
Resumen
La enzima de biosíntesis del cloramfenicol CmlA contiene un grupo único de diirón, distinto de las enzimas relacionadas. Esta diferencia estructural puede influir en su mecanismo de reacción y activación de oxígeno.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- Biología Estructural Biología estructural.
Sus antecedentes:
- La vía biosintética del cloramfenicol depende de enzimas específicas para su función.
- Los clústeres de diirón son sitios activos cruciales en varias metalloenzimas, incluidas las hidroxilasas.
- Comprender la estructura del sitio activo de la enzima es clave para dilucidar los mecanismos de reacción.
Objetivo del estudio:
- Caracterizar la estructura del sitio activo de CmlA, una β-hidroxilasa clave en la biosíntesis del cloramfenicol.
- Para comparar el clúster de diirón en CmlA con los que se encuentran en otras enzimas relacionadas.
- Investigar las posibles implicaciones de las diferencias estructurales en la función enzimática y la activación del oxígeno.
Principales métodos:
- Se empleó la espectroscopia de absorción de rayos X (XAS) para sondear las propiedades electrónicas y estructurales de los centros de hierro.
- Se utilizó la espectroscopia Raman de resonancia para obtener información sobre los modos de vibración y el entorno de coordinación del cúmulo de diirón.
- Se realizaron comparaciones bioinformáticas y estructurales con enzimas homólogas.
Principales resultados:
- CmlA alberga un grupo de (micro-oxo) - (micro-1,3-carboxilato) diironio (III) con centros de hierro de 6 coordenadas.
- La enzima cuenta con 3-4 ligandos de histidina que coordinan los centros de hierro.
- Este sitio activo reside dentro de un pliegue distinto de la β-lactamasa, que difiere del motivo del haz de 4 hélices en la monooxigenasa de metano soluble y enzimas relacionadas.
Conclusiones:
- El clúster de diirón en CmlA posee un entorno estructural y de ligadura único en comparación con otras hidroxilasas de diirón conocidas.
- La divergencia estructural observada, particularmente el conjunto único de pliegues y ligandos, sugiere diferencias potenciales en las especies de oxígeno activado utilizadas por CmlA.
- Se necesitan más estudios para comprender completamente las implicaciones funcionales de la estructura distinta del sitio activo de CmlA en la vía biosintética del cloramfenicol.
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