Figure 5.

Schematic model showing events in which a partially degraded mRNA is released from 70S ribosomes by ssrA RNA charging of the CCA-3′ terminus generated by RNase E with an alanine that promotes trans translation of an ssrA-encoded ORF specifying peptide tag used in proteolysis. 70S ribosomes (indicated as two joining circles), elongating nascent polypeptides (streams of small circles), broken mRNA lacking a stop codon (curved line), carboxyl terminal ssrA-encoded peptide-tag (filled circles), RNA polymerase complex (RNAP), and DNA template are shown. N indicates the NH₂-terminal of peptides. Ala-charged ssrA RNA/tm RNA is shown.