Initiation of translation by cricket paralysis virus IRES requires its translocation in the ribosome.
Bottom Line: By using recent advances in single-particle electron cryomicroscopy, we have solved the structure of CrPV-IRES bound to the ribosome of the yeast Kluyveromyces lactis in both the canonical and rotated states at overall resolutions of 3.7 and 3.8 Å, respectively.In both states, the pseudoknot PKI of the CrPV-IRES mimics a tRNA/mRNA interaction in the decoding center of the A site of the 40S ribosomal subunit.Translocation of the IRES by elongation factor 2 (eEF2) is required to bring the first codon of the mRNA into the A site and to allow the start of translation.
Affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.Show MeSH
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Mentions: Elongation in eukaryotes requires the two GTPase factors eEF1A and eEF2, which are the eukaryotic homologs of EF-Tu and EF-G, respectively. Of these, eEF1A delivers incoming aminoacyl tRNAs as part of a ternary complex with GTP, and eEF2 in the GTP form binds a rotated form of the ribosome and facilitates translocation (Figure 4A). If the CrPV-IRES mimics a pretranslocation state, it should not be able to bind ternary complex initially but should be able to do so after translocation by eEF2 (Figure 4B).
Affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.