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Curso estereoquímico de la reacción catalizada por RimO, una SAM radical metiltriotransferasa

Bradley J Landgraf¹, Squire J Booker¹

¹Department of Chemistry, ‡Department of Biochemistry and Molecular Biology, and §The Howard Hughes Medical Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.

Journal of the American Chemical Society

|February 13, 2016

Resumen

La enzima RimO une un grupo metiltio a la proteína S12. Este estudio revela que RimO extrae el átomo de hidrógeno pro-S del aspartato, un paso clave en su mecanismo dependiente del radical S-adenosilmetionina (SAM).

Área de la Ciencia:

La bioquímica
Enzimología
Biología molecular

Sus antecedentes:

RimO es una enzima radical de S-adenosilmetionina (SAM, por sus siglas en inglés).
Cataliza la metilthiolación del aspartato 89 en la proteína ribosómica S12.
El mecanismo de reacción no estaba claro.

Objetivo del estudio:

Para aclarar el curso estereoquímico de la reacción de RimO.
Investigar el mecanismo de unión del grupo metiltio a la proteína S12.

Principales métodos:

El péptido utilizado imita la proteína S12 con etiquetado de deuterio.
Se ha analizado la transferencia de deuterio a la 5'-deoxyadenosina (5'-dAH).
Efectos del isótopo cinético medido para la abstracción del átomo de hidrógeno.

Principales resultados:

RimO extrae el átomo de hidrógeno pro-S del residuo de aspartilo objetivo.
Se observó un efecto de isótopo cinético de ~ 1.9 para la abstracción H vs. D.
El sistema reductor in vivo (flavodoxina/flavodoxina oxidorreductaza/NADPH) puede suministrar electrones al RimO.

Conclusiones:

El análisis estereoquímico confirma la abstracción de hidrógeno pro-S por RimO.
La extracción de hidrógeno es un paso parcialmente determinante de la velocidad.
RimO puede utilizar sistemas de reducción celular establecidos para su actividad.

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