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Control del potencial redox del citocromo C: la ligadura axial y los efectos del entorno de las proteínas
Gianantonio Battistuzzi1, Marco Borsari, James A Cowan
1Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, Italy.
Journal of the American Chemical Society
|May 9, 2002
Resumen
La investigación de la ligadura del cofactor hemo en el citocromo c y la microperoxidasa-11 (MP11) revela cómo la ligadura axial y la encapsulación de proteínas afectan el potencial de reducción. La exclusión del agua del ambiente hemo es clave para estos cambios termodinámicos.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La electroquímica es electroquímica.
- Química de las proteínas química de las proteínas.
Sus antecedentes:
- El potencial de reducción del citocromo c (E°') es crucial para su función biológica.
- La ligadura axial y el entorno proteico influyen significativamente en las propiedades redox de la proteína hemo.
Objetivo del estudio:
- Investigar cómo la ligadura axial del hierro y la encapsulación de proteínas afectan el potencial de reducción del citocromo c.
- Dividir los cambios en el potencial de reducción en contribuciones entálpicas y entrópicas para el citocromo c y la microperoxidasa-11 (MP11).
Principales métodos:
- Se utilizaron experimentos electroquímicos directos para medir los potenciales de reducción.
- Se emplearon mediciones de temperatura variable para determinar las contribuciones entálpica y entrópica.
- Se llevaron a cabo estudios de unión a los ligandos con imidazol, 2-metil-imidazol, amoníaco, azida y N-acetilmetionina.
Principales resultados:
- La sustitución de Met80 en el citocromo c por ligandos donantes de nitrógeno afecta principalmente el potencial de reducción entálpicamente, estabilizando el estado férrico.
- La unión del ligando al MP11 estabiliza entálpicamente el estado reducido, mientras que la entropía disminuye el potencial de reducción.
- El aumento general en el potencial de reducción de MP11 a citocromo c se atribuye a los términos entálpicos y entrópicos opuestos, dominados por la exclusión de agua.
Conclusiones:
- La ligadura del hemo axial y la encapsulación de proteínas modulan críticamente el potencial de reducción del citocromo c a través de distintos efectos entálpicos y entrópicos.
- La exclusión del agua del ambiente hemo juega un papel dominante en los cambios termodinámicos observados.
- Comprender estos factores proporciona información sobre el ajuste redox de la proteína hemo.
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