Three mechanisms in Escherichia coli rescue ribosomes stalled on non-stop mRNAs: one of them requires release factor 2.

The tmRNA/SmpB system, which is almost universal in bacteria, rescues bacterial ribosomes stalled at the end of non-stop mRNAs (mRNAs lacking a stop codon). In addition, a few bacteria, including Escherichia coli, have developed a second two-component system as reported by Chadani et al. (2012). A small protein, ArfA of 55 amino acids (formerly called YdhL), mediates binding of release factor 2 to the ribosomal A site lacking a complete mRNA codon and thereby triggers translational termination and rescue of the stalled ribosome.