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This article has been peer reviewed. It is the authors' final version prior to publication in The EMBO Journal

Volume 31, March 2012, pages: 1836-1846.

The published version is available at DOI: 10.1038/emboj.2012.22. Copyright © European Molecular Biology Organization


The ribosome recycling factor (RRF) and elongation factor G (EF-G) disassemble the 70S post-termination complex (PoTC) into mRNA, tRNA, and two ribosomal subunits. We have determined cryo-EM structures of the PoTC•RRF complex, with and without EF-G. We find that domain II of RRF initially interacts with universally conserved residues of the 23S rRNA helices 43 and 95, and protein L11 within the 50S ribosomal subunit. Upon EF-G binding, both RRF and tRNA are driven toward the tRNA-exit (E) site, with a large rotational movement of domain II of RRF toward the 30S ribosomal subunit. During this intermediate step of the recycling process, domain II of RRF and domain IV of EF-G adapt unusual conformations. Furthermore, binding of EF-G to the PoTC•RRF complex reverts the ribosome from ratcheted to unratcheted state. These results suggest that (i) the ribosomal intersubunit reorganizations upon RRF binding and subsequent EF-G binding could be instrumental in destabilizing the PoTC, and (ii) the modes of action of EF-G during tRNA translocation and ribosome recycling steps are markedly different.

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