Protein tagging at rare codons is caused by tmRNA action at the 3′ end of nonstop mRNA generated in response to ribosome stalling

SsrA tagging of CRP proteins during translation elongation. (A) Schematic drawing and sequence of plasmid pRH36. The black box is the CRP ORF and the open box represents the region for rare codons inserted. The nucleotide sequence and amino acid sequence (in one-letter code) around this region are shown below the diagram. (B) Western blot analysis of CRP proteins expressed from plasmid pRH36. Lysates equivalent to OD₆₀₀ = 0.1 prepared from TA341 (Δcrp), TA501 (Δcrp ΔssrA), or TA481 (Δcrp ssrA^DD) cells harboring pRH 36 plasmid were analyzed by Western blotting using anti-CRP antibodies.