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Cambios estructurales inducidos por la unión de iones de sodio o litio en el anillo K de la V-ATPasa de Enterococcus
Yuji Furutani1, Takeshi Murata, Hideki Kandori
1Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
Journal of the American Chemical Society
|February 16, 2011
Resumen
La enzima V-ATPasa transporta iones de sodio y litio. La unión iónica causa cambios estructurales clave, como la desprotonación de Glu139, que facilita el transporte eficiente de cationes a través de las membranas.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Transporte de la membrana Transporte de la membrana
Sus antecedentes:
- La V-ATPasa de Enterococcus hirae es un complejo de proteínas de gran tamaño (~700,000 MW).
- Fisiológicamente transporta Na(+) y Li(+) a través de las bicapas lipídicas.
- Estudios anteriores se basaron en la cristalografía de rayos X del dominio del anillo K incrustado en la membrana.
Objetivo del estudio:
- Investigar los cambios estructurales inducidos por la unión iónica en la V-ATPasa intacta en condiciones fisiológicas.
- Para aclarar el papel de los residuos específicos y los cambios de conformación en el transporte catiónico.
Principales métodos:
- Medición de la diferencia inducida por la unión iónica de los espectros infrarrojos (IR) de la V-ATPase. intacta.
- Los experimentos se llevaron a cabo a temperatura fisiológica con una hidratación adecuada.
Principales resultados:
- La unión de iones de sodio o litio induce la desprotonación de Glu139.9.
- Cambios de enlace de hidrógeno observados en un residuo de tirosina.
- Se detectaron cambios conformacionales menores dentro de la estructura del anillo K.
Conclusiones:
- La desprotonación de Glu139 es crucial para el transporte catiónico.
- Las alteraciones estructurales facilitan la reducción de las barreras energéticas para la translocación iónica.
- Estos hallazgos proporcionan información sobre el mecanismo de transporte de cationes por V-ATPase.
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