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Metalotioneínas de dominio único: supermetalización del MT 1a humano
Duncan E K Sutherland1, Mathew J Willans, Martin J Stillman
1Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada.
Journal of the American Chemical Society
|January 17, 2012
Resumen
La metalotioneína humana 1a se une a un octavo ion de cadmio, formando una nueva estructura de un solo dominio. Esta especie "supermetalizada" sugiere un colapso de su estructura de dos dominios, lo que afecta a la homeostasis de zinc y cobre.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Química de las metaloproteínas
Sus antecedentes:
- Las metallotioneinas (MTs) son proteínas ricas en cisteína involucradas en la desintoxicación de los metales, la defensa contra el estrés oxidativo y la homeostasis de los metales esenciales (zinco, cobre).
- Se sabe que la metalotioneína humana 1a (hMT1a) se une hasta con siete iones Zn2+ o Cd2+.
Objetivo del estudio:
- Investigar las consecuencias estructurales del exceso de cadmio (Cd2+)) que se une a la metalotioneína humana en 1a (hMT1a).
- Caracterizar la formación y la estructura de una especie "supermetalizada" Cd(2+) -hMT1a.
Principales métodos:
- Espectrometría de masas de ionización por electrospray (ESI-MS) para determinar el estado de metalización.
- Espectroscopia de dicroísmo circular (CD) para analizar cambios estructurales.
- (113) Espectroscopia de resonancia magnética nuclear (RMN) (directa e indirecta) para elucidar los detalles estructurales.
Principales resultados:
- Formación de una nueva especie Cd(8)-βα-rhMT 1a, indicando la unión de un octavo ion Cd(2+) más allá de la capacidad conocida.
- Cambios significativos en los espectros de CD en la unión de Cd(8), lo que sugiere la pérdida de simetría del racimo y un posible colapso de la estructura de dos dominios.
- (113) Los datos de RMN de Cd indican un perfil espectral simplificado para Cd(8)-βα-rhMT 1a en comparación con Cd(7)-βα-rhMT 1a, lo que apoya la coalescencia estructural.
Conclusiones:
- Las coordenadas del octavo ión Cd2+) a través de la acción concertada de ambos dominios MT, conducen a una potencial estructura de "superdominio" de un solo dominio.
- Esta transición estructural representa un nuevo modo de unión de metales en las metalotioneinas de mamíferos.
- Los hallazgos ofrecen información sobre la plasticidad estructural dinámica de las metalotioneinas en respuesta a la concentración de iones metálicos.
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