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La estructura cristalina de rayos X del protoclorfilurido reductasa independiente de la luz

Norifumi Muraki¹, Jiro Nomata, Kozue Ebata

¹Department of Life Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.

|April 20, 2010

Resumen

La estructura cristalina de la Pchlide oxidoreductasa (DPOR) que actúa en la oscuridad revela un mecanismo para la síntesis de clorofila. Esta enzima similar a la nitrogenasa utiliza una ligación única de aspartato para la actividad catalítica.

Área de la Ciencia:

La bioquímica es la bioquímica.
Biología Estructural Biología estructural.
Investigación de fotosíntesis Investigación de fotosíntesis.

Sus antecedentes:

Los organismos fotosintéticos sintetizan las clorofilas a través de dos vías: la Pchlide oxidoreductasa dependiente de la luz y la Pchlide oxidoreductasa (DPOR) independiente de la luz.
DPOR es una enzima compleja, que comprende la proteína L y la proteína NB, estructuralmente análoga a los componentes de la nitrogenasa.

Objetivo del estudio:

Para determinar la estructura cristalina de la proteína NB de DPOR extraída de Rhodobacter capsulatus. para determinar la estructura cristalina de la proteína NB de DPOR extraída de Rhodobacter capsulatus. para determinar la estructura cristalina de la proteína NB de DPOR extraída de Rhodobacter capsulatus. para determinar la estructura cristalina de la proteína NB de DPOR extraída de Rhodobacter capsulatus. para determinar la estructura cristalina de la proteína NB de DPOR extraída de Rhodobacter capsulatus.
Para dilucidar el mecanismo de la reducción de protoclorfiluro catalizado por DPOR.

Principales métodos:

Cristalografía de rayos X a una resolución de 2.3Å.
Comparación estructural con la proteína nitrogenasa MoFe.

Principales resultados:

La estructura de la proteína NB es similar a la proteína nitrogenasa MoFe, con cada unidad BchN-BchB que contiene protoclorfilurido y un grupo de hierro-azufre (cluster NB).
La ligadura única de aspartato al grupo NB es crucial para la actividad catalítica, no solo para el ensamblaje del grupo.
La unión específica del protoclorfilurido implica el desenrollo de la hélice alfa, lo que facilita un mecanismo de reducción transespecífico.

Conclusiones:

DPOR comparte una arquitectura común con la nitrogenasa para la reducción de multivínculos estables.
Se propone un nuevo mecanismo que involucra al aspartato y al protoclorfillido C17-propionato como donantes de protones para la reducción del doble enlace C17=C18.
Esta visión estructural avanza en la comprensión de la biosíntesis de la clorofila y la catálisis enzimática.

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