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An interaction between the SRP receptor and the translocon is critical during cotranslational protein translocation

The signal recognition particle (SRP)–dependent targeting pathway facilitates rapid, efficient delivery of the ribosome–nascent chain complex (RNC) to the protein translocation channel. We test whether the SRP receptor (SR) locates a vacant protein translocation channel by interacting with the yeast...

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Detalles Bibliográficos
Autores principales: Jiang, Ying, Cheng, Zhiliang, Mandon, Elisabet C., Gilmore, Reid
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 2008
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2290843/
https://www.ncbi.nlm.nih.gov/pubmed/18347066
http://dx.doi.org/10.1083/jcb.200707196
Descripción
Sumario:The signal recognition particle (SRP)–dependent targeting pathway facilitates rapid, efficient delivery of the ribosome–nascent chain complex (RNC) to the protein translocation channel. We test whether the SRP receptor (SR) locates a vacant protein translocation channel by interacting with the yeast Sec61 and Ssh1 translocons. Surprisingly, the slow growth and cotranslational translocation defects caused by deletion of the transmembrane (TM) span of yeast SRβ (SRβ-ΔTM) are exaggerated when the SSH1 gene is disrupted. Disruption of the SBH2 gene, which encodes the β subunit of the Ssh1p complex, likewise causes a growth defect when combined with SRβ-ΔTM. Cotranslational translocation defects in the ssh1ΔSRβ-ΔTM mutant are explained by slow and inefficient in vivo gating of translocons by RNCs. A critical function for translocation channel β subunits in the SR–channel interaction is supported by the observation that simultaneous deletion of Sbh1p and Sbh2p causes a defect in the cotranslational targeting pathway that is similar to the translocation defect caused by deletion of either subunit of the SR.