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Disulfide bridge formation between SecY and a translocating polypeptide localizes the translocation pore to the center of SecY

During their biosynthesis, many proteins pass through the membrane via a hydrophilic channel formed by the heterotrimeric Sec61/SecY complex. Whether this channel forms at the interface of multiple copies of Sec61/SecY or is intrinsic to a monomeric complex, as suggested by the recently solved X-ray...

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Detalles Bibliográficos
Autores principales: Cannon, Kurt S., Or, Eran, Clemons, William M., Shibata, Yoko, Rapoport, Tom A.
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 2005
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2171872/
https://www.ncbi.nlm.nih.gov/pubmed/15851514
http://dx.doi.org/10.1083/jcb.200412019
Descripción
Sumario:During their biosynthesis, many proteins pass through the membrane via a hydrophilic channel formed by the heterotrimeric Sec61/SecY complex. Whether this channel forms at the interface of multiple copies of Sec61/SecY or is intrinsic to a monomeric complex, as suggested by the recently solved X-ray structure of the Methanococcus jannaschii SecY complex, is a matter of contention. By introducing a single cysteine at various positions in Escherichia coli SecY and testing its ability to form a disulfide bond with a single cysteine in a translocating chain, we provide evidence that translocating polypeptides pass through the center of the SecY complex. The strongest cross-links were observed with residues that would form a constriction in an hourglass-shaped pore. This suggests that the channel makes only limited contact with a translocating polypeptide, thus minimizing the energy required for translocation.