Stop codons preceded by rare arginine codons are efficient determinants of SsrA tagging in Escherichia coli.
The SsrA or tmRNA quality control system intervenes when ribosomes stall on mRNAs and directs the addition of a C-terminal peptide tag that targets the modified polypeptide for degradation. Although hundreds of SsrA-tagged proteins can be detected in cells when degradation is prevented, most of these species have not been identified. Consequently, the mRNA sequence determinants that cause ribosome stalling and SsrA tagging are poorly understood. SsrA tagging of Escherichia coli ribokinase occurs at three specific sites at or near the C terminus of this protein. The sites of tagging correspond to ribosome stalling at the termination codon and at rare AGG codons encoding Arg-307 and Arg-309, the antepenultimate and C-terminal residues of E. coli ribokinase. Mutational analyses and studies of the effects of overexpressing the tRNA that decodes AGG reveal that the combination of a rare arginine codon at the C terminus and the adjacent inefficient UGA termination codon act to recruit the SsrA-tagging system, presumably by slowing the rate of translation elongation and termination.
Hayes
Christopher S
CS
Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Bose
Baundauna
B
Sauer
Robert T
RT
D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics*; D001483:Base Sequence; D018388:Codon, Terminator / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012329:RNA, Bacterial / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D012347:RNA, Transfer, Arg / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012270:Ribosomes / Q000378:metabolism
D018388:Codon, Terminator; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012347:RNA, Transfer, Arg; C096222:tmRNA; D001120:Arginine; D017853:Phosphotransferases (Alcohol Group Acceptor); C022534:ribokinase