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Atrapar H- unido al sitio activo de la nitrogenasa FeMo-cofactor durante la evolución de H2: caracterización por

Robert Y Igarashi¹, Mikhail Laryukhin, Patricia C Dos Santos

¹Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA.

Journal of the American Chemical Society

|April 28, 2005

Resumen

Los investigadores descubrieron un nuevo estado S = 1/2 en el cofactor hierro-molibdeno durante la reducción de protones. Este estado implica dos protones/hidruros químicamente equivalentes unidos al cofactor, lo que desafía los modelos existentes.

Área de la Ciencia:

Bioquímica y Biofísica.
Química bioorgánica Química bioorgánica.
Mecanismos de las enzimas Mecanismos enzimáticos

Sus antecedentes:

La nitrogenasa es una enzima crucial que cataliza la fijación del nitrógeno.
El cofactor hierro-molibdeno (FeMo) es el sitio activo de la nitrogenasa.
La comprensión de los intermediarios en la reducción de protones por la nitrogenasa es clave para su mecanismo.

Objetivo del estudio:

Caracterizar un nuevo estado intermedio del cofactor FeMo durante la reducción de protones.
Para aclarar las propiedades estructurales y electrónicas de este estado atrapado S = 1/2.
Investigar la unión y la naturaleza de los protones/hidruros dentro del cofactor FeMo.

Principales métodos:

Se utilizó la espectroscopia (1,2) H-ENDOR (doble resonancia nuclear de electrones).
Realizó gráficos bidimensionales de frecuencia de campo (1) H ENDOR para determinar tensores hiperfinos.
Analizó acoplamientos hiperfinos y propiedades tensoriales para inferir información estructural y química.

Principales resultados:

Se identificó un nuevo estado S = 1/2 en el cofactor FeMo durante la reducción de H+ a H2.
Se reveló la presencia de dos protones/hidruros químicamente equivalentes (H(+/) ((-)) unidos al cofactor.
Se determinaron grandes acoplamientos hiperfinos isotrópicos (aprox. 23 MHz) y simetrías tensoriales para estos hidruros.

Conclusiones:

Los datos no favorecen los modelos que involucran la protonación de sulfuros.
El producto intermedio probablemente contiene dos hidritos unidos químicamente equivalentes, no monohidritos terminales.
Los modelos actuales para la estructura del cofactor FeMo en este estado S = 1/2 requieren revisión.

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