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Las transiciones estructurales sobre la unión de ligandos en una hemoglobina dimérica cooperativa
W E Royer1, W A Hendrickson, E Chiancone
1Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032.
Science (New York, N.Y.)
|August 3, 1990
Resumen
La hemoglobina de las almejas exhibe un mecanismo único de unión de oxígeno cooperativo, distinto de los mamíferos. El análisis estructural revela la comunicación directa del hemo a través de una nueva interfaz, lo que permite la potenciación de la afinidad del oxígeno.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología Estructural
- Ciencia de las proteínas Ciencia de las proteínas.
Sus antecedentes:
- La hemoglobina (Hb) es crucial para el transporte de oxígeno en los vertebrados.
- Las hemoglobinas de mamíferos muestran unión cooperativa al oxígeno a través de cambios estructurales cuaternarios.
- La base estructural de la unión cooperativa del oxígeno en las hemoglobinas de los invertebrados sigue siendo menos comprendida.
Objetivo del estudio:
- Para dilucidar los mecanismos estructurales subyacentes a la unión cooperativa de oxígeno en la hemoglobina de almeja dimérica.
- Para comparar la dinámica estructural de Hb de almeja con Hb de mamíferos en la unión de ligandos.
Principales métodos:
- Determinación de las estructuras cristalinas de alta resolución (2,4 angstrom) de la hemoglobina dimérica de las almejas.
- Estructuras comparadas tanto en estados desoxigenados como en estados ligados por monóxido de carbono (CO).
- Se analizaron los cambios conformacionales en los niveles estructurales terciario y cuaternario.
Principales resultados:
- Identificó una nueva interfaz de subunidad que involucra hélices E y F que facilitan la comunicación directa heme-heme.
- Se observaron cambios estructurales terciarios significativos en la interfaz después de la unión del ligando.
- Los cambios de conformación fueron más pronunciados en el nivel terciario pero más sutiles en el nivel cuaternario en comparación con el Hb. de mamíferos.
Conclusiones:
- La hemoglobina de las almejas emplea un mecanismo estructural distinto para la unión cooperativa del oxígeno.
- La comunicación directa entre los grupos hemo a través de la nueva interfaz es clave para su función.
- Este mecanismo implica reordenamientos terciarios significativos, que vinculan la unión de ligando en una subunidad con una afinidad mejorada en la otra.
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