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Estructura y mecanismo de un transportador de aminoácidos Na+-independiente
Paul L Shaffer1, April Goehring, Aruna Shankaranarayanan
1Vollum Institute, Oregon Health and Science University, 3181 Southwest Sam Jackson Park Road, Portland, OR 97239, USA.
Science (New York, N.Y.)
|July 18, 2009
Resumen
La estructura cristalina del transportador de aminoácidos ApcT revela un mecanismo para el transporte acoplado a protones. Un residuo de lisina, similar al sitio de iones de sodio en otros transportadores, es clave para este proceso.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Transporte de la membrana Transporte de la membrana
Sus antecedentes:
- Los transportadores de aminoácidos, poliaminas y organocation (APC) son transportadores secundarios cruciales involucrados en la absorción de nutrientes, la eliminación de desechos y el mantenimiento del equilibrio celular.
- Comprender la base estructural de la función del transportador APC es vital para descifrar los mecanismos de transporte celular.
Objetivo del estudio:
- Para determinar la estructura cristalina de alta resolución del estado apo de ApcT, un transportador de aminoácidos acoplado a protones.
- Aclarar las características estructurales que subyacen al mecanismo de transporte de ApcT y su relación con otros transportistas secundarios.
Principales métodos:
- Se empleó cristalografía de rayos X para obtener la estructura cristalina de apo-ApcT a una resolución de 2,35 angstroms.
- Se utilizaron análisis bioinformáticos y comparaciones estructurales para identificar los principales residuos funcionales y los principios de transporte conservado.
Principales resultados:
- La estructura cristalina de 2,35 angstrom de apo-ApcT revela un haz de hélice de 12 transmembranas con similitudes estructurales con el transportador LeuT.
- Se identificó un residuo de lisina (Lys-158) en una posición análoga al sitio de unión de iones Na2 en LeuT, lo que sugiere un papel en el acoplamiento de protones.
- La estructura presenta una conformación orientada hacia adentro, característica de un estado ocluido o posterior al transporte.
Conclusiones:
- La estructura de ApcT proporciona información crítica sobre el mecanismo del transporte de aminoácidos acoplados a protones.
- Se propone que la lisina-158 sea central para la translocación de protones, imitando funcionalmente el papel de los iones sodio en transportadores relacionados.
- Este estudio pone de relieve los principios mecánicos conservados entre los transportadores secundarios acoplados a protones y sodio.
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