Cryo-EM structure of the E. coli translating ribosome in complex with SRP and its receptor

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We report the 'early' conformation of the Escherichia coli signal recognition particle (SRP) and its receptor FtsY bound to the translating ribosome, as determined by cryo-EM. FtsY binds to the tetraloop of the SRP RNA, whereas the NG domains of the SRP protein and FtsY interact weakly in this conformation. Our results suggest that optimal positioning of the SRP RNA tetraloop and the Ffh NG domain leads to FtsY recruitment.

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Figure 1: Generation and characterization of RNC–SRP–FtsY.
Figure 2: Atomic model of the early conformation of scSRP.
Figure 3: Cartoon model of co-translational targeting.

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We would like to thank G. Schoehn for collecting EM data, I. Berger for designing scSRP, C. Frick for technical assistance and X. Zhang for helpful suggestions. W. Wintermeyer (Max Planck Institute for Biophysical Chemistry) kindly provided pET24a-Ffh. J. Luirink (Vrije Universiteit Amsterdam) is acknowledged for providing pET9-FtsY. This work was supported by the Swiss National Science Foundation (SNSF) and the National Center of Excellence in Research Structural Biology program of the SNSF. The authors acknowledge support by the Electron Microscopy of ETH Zurich (EMEZ) and from the infrastructure of the Partnership for Structural Biology in Grenoble.

Author information

C.S. conceived the scSRP construct and performed sample preparations; S.-o.S. performed activity assays; D.B. did the electron microscopy; D.B., L.F.E. and C.S. performed the image analysis and model building; C.S., N.B., D.B. and S.-o.S. prepared the manuscript.

Correspondence to Nenad Ban or Christiane Schaffitzel.

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The authors declare no competing financial interests.

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Supplementary Figures 1–5, Supplementary Methods and Supplementary Discussion (PDF 738 kb)

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