Translational termination without a stop codon

Rescuing stalled ribosomes A small percentage of bacterial mRNAs lack a stop codon. Ribosomes stall at the end of such mRNAs, and the buildup of stalled ribosomes can be lethal. The primary rescue mechanism, in which translation continues on a piece of RNA that contains a stop codon, is a drug target. However, bacteria have another backup plan. James et al. present structures that show that ArfA (alternative rescue factor A) substitutes for a stop codon by binding in the ribosomal mRNA channel and recruiting RF2 (release factor 2). It mediates conformational changes required for RF2 to catalyze peptide release. Science , this issue p. 1437