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La unión de ligandos en un sitio de acoplamiento de la citocromo C oxidasa: un estudio de escaneo paso a paso con
Constantinos Koutsoupakis1, Tewfik Soulimane, Constantinos Varotsis
1Department of Chemistry, University of Crete, 71409 Heraklion, Crete, Greece.
Journal of the American Chemical Society
|December 4, 2003
Resumen
El monóxido de carbono (CO) se acopla temporalmente cerca del hemo a) en la citocromo c oxidasa, formando una barrera que impide la reconexión inmediata. Esto revela mecanismos cruciales para el movimiento de ligandos en las enzimas respiratorias.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Las enzimas como la citocromo c oxidasa activan moléculas pequeñas (O(2), NO), lo que requiere una comprensión del movimiento del ligando.
- El transporte de ligandos implica canales y sitios de acoplamiento dentro de la estructura de la enzima.
- El citocromo c oxidasa ba ((3) de T. thermophilus cataliza la reducción de O ((2) y NO.
Objetivo del estudio:
- Para investigar los intermediarios de unión de ligandos en la citocromo c oxidasa a temperatura ambiente.
- Para dilucidar las bases estructurales de la regulación de la reacción en las oxidasas hemo-cobre.
Principales métodos:
- Escaneo paso a paso con resolución de tiempo Espectroscopia infrarroja con transformación de Fourier.
- CO-fotólisis de la citocromo c oxidasa ba(3) obtenida de T. thermophilus.
Principales resultados:
- Se observó que el CO fotolizado quedaba atrapado en un sitio de acoplamiento de ligando cerca del propionato de hemo a3).
- El CO "acoplado" exhibió un estado B(1) (2131 cm(-1)) que persistió durante 35 microsegundos.
- Una barrera proteica transitoria cerca del hemo a(3) inhibió la recombinación de CO durante milisegundos después de la liberación del sitio de acoplamiento.
Conclusiones:
- La citocromo c oxidasa utiliza sitios de acoplamiento específicos para el atrapamiento de ligandos transitorios.
- La reorganización de proteínas alrededor del sitio de acoplamiento crea una barrera temporal para la recombinación de ligandos.
- Este mecanismo es crucial para comprender la dinámica de los ligandos y la respiración en las oxidasas hemo-cobre.
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