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Un movimiento 35-A de miosina del músculo liso en la liberación de ADP
M Whittaker1, E M Wilson-Kubalek, J E Smith
1Department of Cell Biology, Scripps Research Institute, La Jolla, California 92037, USA.
Nature
|December 14, 1995
Resumen
Las proteínas motoras de la miosina II generan fuerza a través de la interacción con la actina. Un dominio rígido de cadena ligera actúa como un brazo de palanca, convirtiendo pequeños cambios en el dominio motor en grandes pasos de 35 angstroms durante la contracción muscular.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
- Fisiología Muscular Fisiología Muscular
Sus antecedentes:
- Las proteínas motoras de la miosina II son cruciales para la contracción muscular, ya que interactúan con los filamentos de F-actina.
- El mecanismo del golpe de fuerza de la miosina, que involucra la hidrólisis de ATP, no se entiende completamente.
- Estudios anteriores sugirieron un movimiento limitado de la cabeza de miosina (S1) en la actina durante el ciclismo de cruce de puente.
Objetivo del estudio:
- Para aclarar la base estructural del mecanismo de golpe de fuerza de la miosina.
- Investigar el papel del dominio de la miosina S1 y el dominio de unión de la cadena ligera en la generación de fuerza.
- Para determinar los cambios conformacionales en la miosina durante la hidrólisis de ATP y la unión a la actina.
Principales métodos:
- Se utilizó microscopía crioelectrónica tridimensional (3D) (cryo-EM) para mapear las estructuras de F-actina decoradas con S1.
- Se determinaron estructuras en presencia y ausencia de MgADP para capturar diferentes estados del motor de miosina.
- El análisis estructural detallado comparó las orientaciones del dominio motor de la miosina y del dominio de unión de la cadena ligera.
Principales resultados:
- La estructura del dominio motor de la miosina se mantuvo en gran medida consistente entre los estados ligados y no ligados a MgADP.
- Se observaron diferencias de orientación significativas en el dominio de unión de cadenas ligeras.
- El dominio de unión de la cadena ligera funciona como un brazo de palanca rígido, girando aproximadamente 23 grados.
- Este pivote da como resultado un tamaño de paso sustancial de aproximadamente 35 angstroms.
Conclusiones:
- El golpe de potencia de la miosina es impulsado principalmente por el giro del dominio de unión de la cadena ligera, no por grandes cambios conformacionales en el dominio motor.
- Los cambios conformacionales mediados por nucleótidos en el dominio motor de la miosina son amplificados por el dominio de la cadena ligera para producir grandes pasos de movimiento.
- Este mecanismo de palanca-brazo explica cómo la miosina genera una fuerza eficiente para la contracción muscular y la motilidad celular.
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