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Publication Abstract from PubMed

During normal translation, the binding of a release factor to one of the three stop codons (UGA, UAA or UAG) results in the termination of protein synthesis. However, modification of the initial uridine to a pseudouridine (Psi) allows efficient recognition and read-through of these stop codons by a transfer RNA (tRNA), although it requires the formation of two normally forbidden purine-purine base pairs. Here we determined the crystal structure at 3.1 A resolution of the 30S ribosomal subunit in complex with the anticodon stem loop of tRNASer bound to the PsiAG stop codon in the A site. The PsiA base pair at the first position is accompanied by the formation of purine-purine base pairs at the second and third positions of the codon, which show an unusual Watson-Crick/Hoogsteen geometry. The structure shows a previously unsuspected ability of the ribosomal decoding centre to accommodate non-canonical base pairs.

Unusual base pairing during the decoding of a stop codon by the ribosome.,Fernandez IS, Ng CL, Kelley AC, Wu G, Yu YT, Ramakrishnan V Nature. 2013 Jun 30. doi: 10.1038/nature12302. PMID:23812587^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.