Biology Newsfeed

[Report] Translational termination without a stop codon

ScienceNOW - Fetched: December 15th, 2016, 2:00pm UTC

Ribosomes stall when they encounter the end of messenger RNA (mRNA) without an in-frame stop codon. In bacteria, these “nonstop” complexes can be rescued by alternative ribosome-rescue factor A (ArfA). We used electron cryomicroscopy to determine structures of ArfA bound to the ribosome with 3′-truncated mRNA, at resolutions ranging from 3.0 to 3.4 angstroms. ArfA binds within the ribosomal mRNA channel and substitutes for the absent stop codon in the A site by specifically recruiting release factor 2 (RF2), initially in a compact preaccommodated state. A similar conformation of RF2 may occur on stop codons, suggesting a general mechanism for release-factor–mediated translational termination in which a conformational switch leads to peptide release only when the appropriate signal is present in the A site. Authors: Nathan R. James, Alan Brown, Yuliya Gordiyenko, V. Ramakrishnan

Read more

Return to the Newsfeed