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La inserción de arginina mediada por fosfato en las membranas lipídicas y la formación de poros por un péptido de
Ming Tang1, Alan J Waring, Mei Hong
1Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
Journal of the American Chemical Society
|August 21, 2007
Resumen
Los residuos cargados se insertan en las bicapas lipídicas a través de las interacciones guanidinio-fosfato, formando poros toroidales. Este mecanismo, observado en los péptidos antimicrobianos, implica que los residuos de arginina catiónica tiran de los fosfatos aniónicos hacia el núcleo de la membrana.
Área de la Ciencia:
- La biofísica es la biofísica.
- Biofísica de las membranas Biofísica de las membranas.
- La bioquímica es la bioquímica.
Sus antecedentes:
- Los residuos de aminoácidos cargados en las bicapas de lípidos hidrofóbicos son energéticamente desfavorables.
- Los péptidos de membrana catiónica y los dominios de proteínas a menudo insertan residuos cargados en las bicapas lipídicas.
- El mecanismo de la translocación de residuos cargados a través de las bicapas lipídicas sigue sin estar claro.
Objetivo del estudio:
- Para dilucidar el mecanismo de la translocación de residuos cargados a través de las bicapas lipídicas.
- Para investigar la interacción entre los péptidos ricos en arginina y las membranas lipídicas.
- Para proporcionar evidencia directa de la formación de poros toroidales.
Principales métodos:
- Espectroscopia de Resonancia Magnética Nuclear (RMN) de estado sólido para medir las distancias (13) C-(31) P.
- Mediciones del ángulo de torsión para confirmar la conformación del péptido.
- Fase de gel (1) Difusión de espín H para evaluar la ubicación del péptido dentro de la membrana.
Principales resultados:
- Se midieron distancias cortas (13) C-(31) P (4.0-8.0 A) para múltiples residuos de arginina en el péptido dentro de las membranas lipídicas.
- Evidencia de la formación de enlaces de hidrógeno N-H...O-P entre los grupos arginina y fosfato.
- Confirmación de una conformación transmembrana beta-hairpin para el péptido.
- Evidencia directa de la formación de poros toroidales, donde los grupos de fosfato lipídico están incrustados en el núcleo de la membrana hidrofóbica.
Conclusiones:
- La complejación de guanidinio-fosfato impulsa la inserción de residuos de arginina catiónica en el núcleo de la membrana hidrofóbica.
- Esta translocación mediada por fosfato de iones de guanidinio es un mecanismo clave para la formación de poros toroidales.
- Los hallazgos sugieren que este mecanismo es relevante para otros péptidos antimicrobianos ricos en arginina y proteínas de membrana catiónica.
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