title: Characterization of YafO, an Escherichia coli toxin.
abstract: YafO is a toxin encoded by the yafN-yafO antitoxin-toxin operon in the Escherichia coli genome. Our results show that YafO inhibits protein synthesis but not DNA or RNA synthesis. The in vivo [35S]methionine incorporation was inhibited within 5 min after YafO induction. In in vivo primer extension experiments with two different mRNAs, the specific cleavage bands appeared 11-13 bases downstream of the initiation codon, AUG, 2.5 min after the induction of YafO. An identical band was also detected in in vitro toeprinting experiments when YafO was added to the reaction mixture containing 70 S ribosomes and the same mRNAs even in the absence of tRNA(f)(Met). Notably, this band was not detected in the presence of YafO alone, indicating that YafO by itself does not have endoribonuclease activity under the conditions used. The full-length mRNAs almost completely disappeared 30 min after YafO induction in in vivo primer extension experiments, consistent with Northern blotting analysis. Over 84% of [35S]methionine-tRNA(f)(Met) was released from the translation initiation complex at 5.43 microM YafO in vitro. We demonstrated that the 70 S ribosome peak significantly increased upon YafO induction, and when the 70 S ribosomes dissociated into 50 and 30 S subunits, YafO was found to be associated with 50 S subunits. These results demonstrate that YafO is a ribosome-dependent mRNA interferase inhibiting protein synthesis.
authors.affiliation: Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
authors.forename: Yonglong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Masayori
authors.initials: M
authors.lastname: Inouye
mesh_terms: D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D018387:Codon, Initiator / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D009876:Operon / Q000502:physiology*; D014176:Protein Biosynthesis / Q000502:physiology*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000235:genetics / Q000378:metabolism; D054681:Ribosome Subunits, Large, Bacterial / Q000235:genetics / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D018387:Codon, Initiator; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; C544331:YafO protein, E coli