Secondary structures of mutant tmRNAs from E. coli and M. tuberculosis . (A) Ec tmRNA(H8). (B) Mt tmRNA(H6). The 5’-to-3’ direction of the tmRNA chain is indicated by lines with open arrowheads. Nucleotides are labeled with dots in increments of ten. Four pseudoknots, the open reading frame, the tRNA-like domain, and helix 5 are denoted pk1-pk4, ORF, TLD, and hp5, respectively. Four segments of helix 2 are shown as 2a-2d. Resume codons GCA and GCC are underlined. An arrow marks the stop codon. Mutant peptide tags ANHHHHHHHH and ADSHQRHHHHHH are highlighted.