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Estructura del transportador de vitamina B12 BtuCD-F unido a la AMP y la PNP
Vladimir M Korkhov1, Samantha A Mireku, Kaspar P Locher
1Institute of Molecular Biology and Biophysics, ETH Zürich, CH-8093 Zürich, Switzerland.
Nature
|September 25, 2012
Resumen
El transportador de la cassette de unión de ATP (ABC) BtuCD, crucial para la absorción de vitamina B12 en E. coli, revela un nuevo mecanismo de transporte. Los estudios estructurales y funcionales revelan un estado intermedio único y un movimiento peristáltico, distinto de otros transportadores ABC.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Microbiología Microbiología.
Sus antecedentes:
- El transportador BtuCD de la cassette de unión al ATP (ABC) facilita la absorción de la vitamina B12 en Escherichia coli.
- Estudios estructurales previos aclararon los estados apo, pero no el mecanismo de transporte.
Objetivo del estudio:
- Para dilucidar el mecanismo de transporte de BtuCD mediante la determinación de la estructura de un estado intermedio funcional.
Principales métodos:
- 3.5 Å determinación de la estructura cristalina del complejo BtuCD-BtuF unido a AMP-PNP.
- Ensayos de captura de radioligandos. ensayos de captura de radioligandos.
- Ensayos de ingeniería de enlaces cruzados de disulfuro y ensayos funcionales.
Principales resultados:
- Una nueva conformación de las subunidades BtuC reveló una puerta citoplasmática sellada, formando una cavidad cerrada.
- Esta cavidad, ubicada a mitad de camino a través de la membrana, alberga la vitamina B12.
- El complejo BtuCD-F se une a la vitamina B12 en presencia de AMP-PNP.
Conclusiones:
- Los hallazgos sugieren un inesperado mecanismo de transporte peristáltico para la vitamina B12.
- Este mecanismo difiere significativamente de los observados en otros transportadores ABC.
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