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Simulaciones moleculares de microsegundos revelan una vía de protones transitorios en la bomba de calcio

L Michel Espinoza-Fonseca¹, G Lizbeth Ramírez-Salinas²

¹†Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States.

Journal of the American Chemical Society

|June 2, 2015

Resumen

La bomba de Ca2+-ATPasa (SERCA) del retículo sarcoplasmático utiliza una vía de protones transitorios durante los cambios estructurales rápidos. Esta vía optimiza el transporte de calcio y preserva la estabilidad de la bomba al neutralizar los sitios cargados.

Área de la Ciencia:

La bioquímica es la bioquímica.
Biología Estructural Biología estructural.
Transporte de la membrana Transporte de la membrana

Sus antecedentes:

El retículo sarcoplasmático Ca2+-ATPasa (SERCA) es crucial para la contracción muscular, transportando los iones Ca2+ y H2+.
SERCA utiliza vías separadas para el transporte de iones para mantener la integridad estructural.
La existencia de trayectorias iónicas simultáneas durante las transiciones estructurales rápidas sigue sin estar clara.

Objetivo del estudio:

Investigar la presencia y la función de las vías simultáneas de protones e iones metálicos durante las transiciones estructurales rápidas (microsegundos) en SERCA.
Para dilucidar el mecanismo de transporte de protones durante los rápidos cambios de conformación SERCA.

Principales métodos:

Análisis de las trayectorias de dinámica molecular de microsegundos de largo de un intermediario SERCA protonado (E1·H(+) 771).
Identificación y caracterización de un poro hidrofóbico transitorio utilizando el análisis estructural.
Cálculos de la proteína pKa para evaluar la idoneidad del poro para el transporte de protones.

Principales resultados:

Se identificó un poro hidrofóbico transitorio en el lado luminal de las hélices transmembrana 6, 8 y 9.
Este poro conecta el sitio de transporte con el lumen a través de moléculas de agua, facilitando el transporte de protones.
El poro es adecuado para el transporte de protones, como lo indican el análisis estructural y los cálculos de pKa.

Conclusiones:

Existe una vía de protones transitorios en SERCA, activa durante las rápidas transiciones estructurales.
Esta vía neutraliza los sitios de transporte, preservando la estabilidad de SERCA y optimizando el transporte de Ca2+.
Los hallazgos ofrecen información sobre los mecanismos de intercambio iónico en las ATPasas de tipo P a través de poros hidrofóbicos transitorios.

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