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Caracterización estructural de un ensamblado paramagnético de iones metálicos en espiral alfa helicoidal de tres
Miriam Gochin1, Valentina Khorosheva, Martin A Case
1Contribution from the Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143, USA. miriam@picasso.nmr.ucsf.edu
Journal of the American Chemical Society
|September 13, 2002
Resumen
Un péptido modificado forma una bobina en espiral estable con iones metálicos. Este haz de hélice muestra un N-terminal dinámico y un C-terminal estructurado, revelando conformaciones duales influenciadas por los residuos de leucina.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Química del péptido Química del péptido
Sus antecedentes:
- Los péptidos diseñados con núcleos de leucina pueden formar estructuras helicoidales.
- La oligomerización de péptidos es a menudo dependiente de la concentración y puede estar mal definida.
- La modificación covalente puede alterar el plegamiento y la estabilidad del péptido.
Objetivo del estudio:
- Para investigar las propiedades estructurales de un péptido helicoidal modificado.
- Determinar el papel de los iones metálicos de transición en la estabilización de los conjuntos de péptidos.
- Para dilucidar la dinámica conformacional del haz de hélice resultante.
Principales métodos:
- Espectroscopia de Resonancia Magnética Nuclear (RMN) utilizando iones paramagnéticos de Ni2+ y Co2+.
- Análisis de los Efectos de Rehabilitación Nuclear (NOE) para la determinación estructural.
- Interpretación de los desplazamientos de pseudocontacto del protón (1H) para identificar las formas isoméricas.
Principales resultados:
- La unión de iones metálicos está estrechamente acoplada con el plegamiento de la hélice.
- La bobina enrollada paralela de tres hilos exhibe una región N-terminal dinámica y una mitad C-terminal estructurada.
- Se identificaron dos isómeros faciales distintos con diferentes tensores de susceptibilidad, lo que indica una doble conformación.
Conclusiones:
- Los iones de metales de transición estabilizan efectivamente el péptido en un haz definido de tres hélices.
- La región N-terminal del haz de hélice es dinámica conformacionalmente.
- Las cadenas laterales de leucina en la posición 3 influyen en la variación conformacional N-terminal observada y el isomerismo.
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