Conformational Control of Translation Termination on the 70S Ribosome

Translation termination ensures proper lengths of cellular proteins. During termination, release factor (RF) recognizes a stop codon and catalyzes peptide release. Conformational changes in RF are thought to underlie accurate translation termination. However, structural studies of ribosome termination complexes have only captured RFs in a conformation that is consistent with the catalytically active state. Here, we employ a hyper-accurate RF1 variant to obtain crystal structures of 70S termination complexes that suggest a structural pathway for RF1 activation. We trapped RF1 conformations with the catalytic domain outside of the peptidyl-transferase center, while the codon-recognition domain binds the stop codon. Stop-codon recognition induces 30S decoding-center rearrangements that precede accommodation of the catalytic domain. The separation of codon recognition from the opening of the catalytic domain suggests how rearrangements in RF1 and in the ribosomal decoding center coordinate stop-codon recognition with peptide release, ensuring accurate translation termination. [Display omitted] •RF1 with shorter switch loop (Δ302-304) potently discriminates against sense codons•Codon-recognition domain 2 of RF1 binds 70S while catalytic domain 3 is disengaged•Decoding-center rearrangements upon RF1 binding occur prior to GGQ docking•Conformational change in RF1 couples stop-codon recognition with peptide release Accurate translation termination defines the lengths of cellular proteins, ensuring proteome integrity. Release factors recognize a stop codon and hydrolyze peptidyl-tRNA, releasing the newly made protein from the ribosome. Here, 70S termination structures capture release factor RF1 in pre-accommodation-like conformations, shedding light on the mechanism of termination accuracy.