Structure of the Quaternary Complex Between SRP, SR, and Translocon Bound to the Translating Ribosome

Overview

Journal Nat Commun

Specialty Biology

Date 2017 May 20

PMID 28524878

Citations 25

Authors

Ahmad Jomaa

Yu-Hsien Hwang Fu

Daniel Boehringer

Marc Leibundgut

Shu-Ou Shan

Nenad Ban

Affiliations

Soon will be listed here.

Abstract

During co-translational protein targeting, the signal recognition particle (SRP) binds to the translating ribosome displaying the signal sequence to deliver it to the SRP receptor (SR) on the membrane, where the signal peptide is transferred to the translocon. Using electron cryo-microscopy, we have determined the structure of a quaternary complex of the translating Escherichia coli ribosome, the SRP-SR in the 'activated' state and the translocon. Our structure, supported by biochemical experiments, reveals that the SRP RNA adopts a kinked and untwisted conformation to allow repositioning of the 'activated' SRP-SR complex on the ribosome. In addition, we observe the translocon positioned through interactions with the SR in the vicinity of the ribosome exit tunnel where the signal sequence is extending beyond its hydrophobic binding groove of the SRP M domain towards the translocon. Our study provides new insights into the mechanism of signal sequence transfer from the SRP to the translocon.

Citing Articles

The SecM arrest peptide traps a pre-peptide bond formation state of the ribosome.

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Spatiotemporal kinetics of the SRP pathway in live cells.

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