Research ArticleSTRUCTURAL BIOLOGY

Ribosome rearrangements at the onset of translational bypassing

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Science Advances  07 Jun 2017:
Vol. 3, no. 6, e1700147
DOI: 10.1126/sciadv.1700147

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Abstract

Bypassing is a recoding event that leads to the translation of two distal open reading frames into a single polypeptide chain. We present the structure of a translating ribosome stalled at the bypassing take-off site of gene 60 of bacteriophage T4. The nascent peptide in the exit tunnel anchors the P-site peptidyl-tRNAGly to the ribosome and locks an inactive conformation of the peptidyl transferase center (PTC). The mRNA forms a short dynamic hairpin in the decoding site. The ribosomal subunits adopt a rolling conformation in which the rotation of the small subunit around its long axis causes the opening of the A-site region. Together, PTC conformation and mRNA structure safeguard against premature termination and read-through of the stop codon and reconfigure the ribosome to a state poised for take-off and sliding along the noncoding mRNA gap.

Keywords
  • translation
  • ribosome
  • bypassing
  • recoding
  • structure

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