Abstract
SummaryIn eukaryotes, accurate protein synthesis relies on a family of translational GTPases that pair with specific decoding factors to decipher the mRNA code on ribosomes. We present structures of the mammalian ribosome engaged with decoding factor⋅GTPase complexes representing intermediates of translation elongation (aminoacyl-tRNA⋅eEF1A), termination (eRF1⋅eRF3), and ribosome rescue (Pelota⋅Hbs1l). Comparative analyses reveal that each decoding factor exploits the plasticity of the ribosomal decoding center to differentially remodel ribosomal proteins and rRNA. This leads to varying degrees of large-scale ribosome movements and implies distinct mechanisms for communicating information from the decoding center to each GTPase. Additional structural snapshots of the translation termination pathway reveal the conformational changes that choreograph the accommodation of decoding factors into the peptidyl transferase center. Our results provide a structural framework for how different states of the mammalian ribosome are selectively recognized by the appropriate decoding factor⋅GTPase complex to ensure translational fidelity.
Highlights
Successful protein synthesis by ribosomes requires amino acids to be incorporated correctly during polypeptide elongation, translation to terminate at precise points, and quality control pathways to be engaged when translation is interrupted (Dever and Green, 2012)
To prepare the elongation complex, ongoing in vitro translation reactions in rabbit reticulocyte lysate of an N-terminally tagged protein were inhibited by the elongation inhibitor didemnin B (Rinehart et al, 1981), and the ribosome-nascent chains (RNCs) were affinity purified via the partially synthesized nascent polypeptide
To generate the termination complex, we programmed and affinity purified RNCs with a UGA stop codon in the A site that were reconstituted with eRF1, eRF3, and the nonhydrolyzable GTP analog GMPPCP
Summary
The individual decoding factor,GTPase complexes involved in protein synthesis differentially remodel local protein and RNA elements on ribosomes to ensure translation fidelity. Highlights d Cryo-EM structures of elongating, terminating, and stalled mammalian ribosomes d Eukaryotic-specific elements contribute to stringent sense and stop codon decoding d Pelota engages stalled ribosomes by destabilizing mRNA in the mRNA channel d Decoding complexes communicate recognition to GTPase activation in different ways. 2016, Cell 167, 1229–1240 November 17, 2016 a 2016 MRC Laboratory of Molecular Biology.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
