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Asimetría en la estructura del complejo proteico de unión al transportador ABC BtuCD-BtuF
Rikki N Hvorup1, Birke A Goetz, Martina Niederer
1Institute of Molecular Biology and Biophysics, ETH Zurich, HPK D14.3, 8093 Zurich, Switzerland.
Science (New York, N.Y.)
|August 4, 2007
Resumen
La estructura del complejo BtuCD-F revela cambios conformacionales significativos en el transporte de vitamina B12 por Escherichia coli. Esta estructura puede representar un intermediario de post-translocación en el mecanismo de transporte de la cassette de unión al trifosfato de adenosina.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Microbiología Molecular Microbiología Molecular.
Sus antecedentes:
- BtuCD es un transportador de adenosina trifosfato en casete de unión (ABC) crucial para la absorción de vitamina B12 en Escherichia coli.
- La vitamina B12 se transloca desde la proteína de unión periplásmica BtuF al citoplasma a través de BtuCD.
Objetivo del estudio:
- Para aclarar el mecanismo estructural de la translocación de la vitamina B12 por el complejo BtuCD-F.
- Para investigar los cambios conformacionales durante el ciclo de transporte del transportador BtuCD-F.
Principales métodos:
- Cristalografía de rayos X para determinar la estructura de 2,6 angstroms del complejo BtuCD-F.
- Espectroscopia de resonancia paramagnética de electrones (EPR) de mutantes de cisteína con etiqueta de espín en los proteoliposomas.
Principales resultados:
- La estructura BtuCD-F muestra alteraciones conformacionales sustanciales en comparación con las estructuras BtuCD y BtuF individuales.
- Se observó un desplazamiento significativo de la vitamina B12 desde el bolsillo de unión BtuF y conformaciones distintas de las subunidades BtuC.
- Se encontró que la vía de translocación estaba cerrada en ambos lados de la membrana en la estructura determinada.
- Los datos de EPR apoyan la conformación de la estructura cristalina, lo que sugiere un estado posterior a la translocación.
Conclusiones:
- La estructura determinada del complejo BtuCD-F proporciona información sobre la dinámica conformacional de los transportadores ABC.
- Los hallazgos sugieren que la estructura BtuCD-F representa un intermediario posterior a la translocación, ofreciendo una instantánea del ciclo de transporte.
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