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La desfosforilación de la bomba de calcio acoplada a la contraoclusión de contraion
Claus Olesen1, Thomas Lykke-Møller Sørensen, Rikke Christina Nielsen
1Centre for Structural Biology, Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Science (New York, N.Y.)
|December 25, 2004
Resumen
Las ATPasas de tipo P utilizan la hidrólisis del trifosfato de adenosina (ATP) para impulsar el transporte de iones. Los investigadores revelaron una estructura cristalina que muestra cómo se ocluyen los contradiones de protones durante el transporte de calcio, aclarando la enzima.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- La biofísica molecular es la biofísica molecular.
Sus antecedentes:
- Las ATPasas de tipo P son proteínas de membrana cruciales que utilizan la hidrólisis del trifosfato de adenosina (ATP) para transportar iones activamente a través de las membranas celulares.
- Este proceso implica la formación y descomposición de un intermediario de fosfoenzima covalente, impulsando el transporte de cationes y el contra transporte.
Objetivo del estudio:
- Para determinar la estructura cristalina del retículo sarcoplasmático del conejo Ca2+ adenosina trifosfatasa (SERCA) en complejo con fluoruro de aluminio.
- Para dilucidar el mecanismo de los estados de transición ocluidos durante el transporte de Ca2+ y el contra transporte de H+ acoplados a la hidrólisis de ATP.
Principales métodos:
- Se empleó cristalografía de rayos X para obtener la estructura cristalina de la Ca2+ ATPasa en un complejo de imitación del estado de transición.
- El análisis de datos bioquímicos se integró con los hallazgos estructurales para interpretar el estado funcional de la enzima.
Principales resultados:
- La estructura cristalina reveló un complejo de Ca2+ ATPasa con fluoruro de aluminio, imitando el estado de transición de la fosfoenzima hidrólisis.
- Esta estructura representa un estado ocluido para los protones, lo que sugiere un paso clave en el ciclo de transporte.
- El motivo Thr-Gly-Glu-Ser conservado fue identificado como el sitio catalítico para la hidrólisis, empleando un mecanismo de reacción nucleofílico asociativo.
Conclusiones:
- Se propone un mecanismo general para los estados de transición ocluidos en el transporte de Ca2+ junto con el contra transporte de H+.
- Los hallazgos proporcionan información sobre los pasos de fosforilación y desfosforilación acoplados críticos para la función de la ATPasa de tipo P.
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