Ribosomes containing the C1054-deletion mutation in E. coli 16S rRNA act as suppressors at all three nonsense codons

It was established some time ago that the deletion of base C1054 in E. coli 16S rRNA specifically affects UGA-dependent termination of translation. Based on this observation, a model for the termination event was proposed in which the UGA nonsense codon on the mRNA base-pairs with a complementary motif in 'helix 34' of the 16S rRNA, thus potentially providing a recognition signal for the binding of the release factor. This model has been re-examined here and evidence is presented which demonstrates that ribosomes containing the C1054 delta mutation enhance the activity of suppressors of both UAG and UAA termination codons introduced into the host. The results do not support the nonsense codon-16S rRNA base pairing model, and rather imply a more general involvement of 'helix 34' in the translation termination reactions.