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Inversión de la topología de membrana de SecG junto con la translocación de preproteína dependiente de SecA
K Nishiyama1, T Suzuki, H Tokuda
1Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
Cell
|April 5, 1996
Resumen
La inversión de la topología de la proteína SecG es crucial para la eficiencia de la translocación de la preproteína de E. coli. Este proceso está acoplado a los ciclos SecA y es esencial para la translocación de proteínas a través de las membranas.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Biología celular Biología celular.
- La bioquímica es la bioquímica.
Sus antecedentes:
- La translocación de la preproteína de E. coli, compuesta por SecA y el complejo SecY/E/G, facilita el transporte de proteínas a través de la membrana interna.
- SecA utiliza ciclos impulsados por ATP de inserción y desinserción de la membrana para entregar preproteínas al canal SecY/E.
- SecG mejora significativamente la eficiencia de este sistema de translocación.
Objetivo del estudio:
- Para investigar el papel de SecG en la translocación de las preproteínas.
- Para dilucidar el comportamiento dinámico y la topología de SecG durante la translocación.
- Comprender el acoplamiento funcional entre SecG, SecA y el mecanismo de translocación.
Principales métodos:
- Utilizó anticuerpos contra la región C-terminal del SecG para probar su accesibilidad.
- Empleó vesículas de membrana everteadas de E. coli.
- Hidrólisis manipulada de ATP para bloquear y observar los intermediarios de la translocación.
Principales resultados:
- Un anticuerpo dirigido al extremo C del SecG inhibió la translocación, lo que indica su participación.
- La región C-terminal de SecG cambió de un estado de exposición interna a un estado de exposición externa tras el bloqueo de translocación después de la iniciación.
- Una región distinta de SecG exhibió una inversión de topología, fuertemente acoplada a la translocación y al ciclo de inserción-desinserción de SecA.
Conclusiones:
- SecG sufre una inversión de topología durante la translocación preproteína.
- Este cambio conformacional dinámico en SecG es esencial para la eficiencia de la translocación.
- El ciclo funcional de SecG está intrínsecamente relacionado con la actividad dependiente de ATP de SecA.
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