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El papel de la electrostática en el reconocimiento del sideróforo por la inmunoproteína siderocalina
Trisha M Hoette1, Rebecca J Abergel, Jide Xu
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Journal of the American Chemical Society
|December 5, 2008
Resumen
La siderocalina se une a los sideróforos bacterianos para bloquear la absorción de hierro. Las interacciones electrostáticas, no los choques estéricos, dictan la fuerza de unión cuando los sideróforos carecen de incompatibilidades estructurales.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Inmunología Inmunología.
- Microbiología Microbiología.
Sus antecedentes:
- El hierro es crucial para la virulencia bacteriana, requiriendo sideróforos para la adquisición de hierro en los huéspedes.
- La siderocalina es una proteína humana que se une a los sideróforos para inhibir la captación de hierro y la virulencia bacteriana.
- Los choques estéricos y las interacciones electrostáticas influyen en la unión de los sideróforos por Siderocalin.
Objetivo del estudio:
- Desconvolucionar la contribución de las interacciones electrostáticas al reconocimiento de sideróforos por Siderocalin.
- Investigar el papel de las interacciones carga-carga y catión-pi en la unión de los sideróforos de 2,3-catecolatos.
- Comprender cómo las variaciones en la estructura de los sideróforos afectan la afinidad de unión a la siderocalina.
Principales métodos:
- Síntesis de análogos de enterobactina isostéricos con diferentes unidades de 2,3-catecolamida (CAM) y N-hidroxipiridinonato (1,2-HOPO).
- Cristalografía de moléculas pequeñas para determinar la complementariedad de forma de los análogos.
- Ensayos de unión basados en fluorescencia para medir afinidades de unión.
- Ab initio cálculos para modelar las propiedades electrostáticas.
Principales resultados:
- Todos los análogos sintetizados caben dentro de la bolsa de unión de Siderocalin.
- Los complejos sideróforos férricos con menos unidades CAM exhibieron afinidades de unión significativamente más bajas.
- La afinidad de unión disminuyó a medida que el número de unidades CAM disminuyó (valores de K (d) de >600 nM a 0.3 nM).
Conclusiones:
- Las interacciones electrostáticas son determinantes críticos de la fuerza de unión del sideróforo a la siderocalina en ausencia de choques estéricos.
- El número de unidades de 2,3-catecolamida se correlaciona directamente con la afinidad de unión de los análogos sideróforos.
- Este estudio aclara los mecanismos electrostáticos subyacentes al reconocimiento de sideróforos por Siderocalin.
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