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Un estudio IR de los cambios de protonación asociados con la transferencia de electrones hemo-hemo en la citocromo c

Masayo Iwaki¹, Peter R Rich

¹Glynn Laboratory of Bioenergetics, Department of Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.

Journal of the American Chemical Society

|February 17, 2007

Resumen

La investigación de los cambios de la espectroscopia infrarroja en la citocromo c oxidasa bovina revela eventos de protonación dependientes del pH que influyen en la transferencia de electrones. Se identifica un grupo titulable con pK 8.2 y otro por encima de 9, lo que afecta la función enzimática.

Área de la Ciencia:

La bioquímica es la bioquímica.
La espectroscopia es una técnica de espectroscopia.
La cinética de las enzimas.

Sus antecedentes:

La citocromo c oxidasa bovina es una enzima clave en la respiración celular.
La espectroscopia infrarroja (IR) se utiliza para estudiar los cambios moleculares.
La fotólisis del monóxido de carbono (CO) es una técnica para iniciar estados transitorios en las metalloenzimas.

Objetivo del estudio:

Para investigar los cambios espectrales infrarrojos (IR) en la citocromo c oxidasa bovina después de la fotólisis del CO.
Para dilucidar el papel del pH y la protonación en la transferencia inversa de electrones dentro de la enzima.
Para identificar grupos titulables involucrados en la modulación de la actividad enzimática.

Principales métodos:

Se empleó espectroscopia infrarroja (IR) para monitorear los cambios espectrales.
Los experimentos se llevaron a cabo en un rango de pH/pD de 6-9.8.
El intercambio de H2O/D2O y la comparación con los datos cristalográficos existentes ayudaron a las asignaciones de banda.

Principales resultados:

Se observaron cambios espectrales de IR debido tanto a la fotólisis de CO como a la posterior transferencia de electrones inversa.
Se identificó un componente independiente del pH vinculado a los ácidos carboxílicos protonados (pK ~ 8.2).
Se observó un componente dependiente del pH, asociado con la perturbación de la arginina (pK >9), que potencialmente involucra Arg-438.

Conclusiones:

La transferencia de electrones inversa en la citocromo c oxidasa involucra componentes independientes del pH y dependientes del pH.
Los grupos titulables específicos, incluidos los ácidos carboxílicos y los residuos de arginina, juegan un papel crucial en la modulación de la transferencia de electrones.
Estos hallazgos proporcionan información sobre el significado funcional de los residuos específicos en la catálisis enzimática.

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