title: The inhibitory mechanism of protein synthesis by YoeB, an Escherichia coli toxin.
abstract: YoeB is a toxin encoded by the yefM-yoeB antitoxin-toxin operon in the Escherichia coli genome. Here we show that YoeB, a highly potent protein synthesis inhibitor, specifically blocks translation initiation. In in vivo primer extension experiments using two different mRNAs, a major band was detected after YoeB induction at three bases downstream of the initiation codon at 2.5 min. An identical band was also detected in in vitro toeprinting experiments after the addition of YoeB to the reaction mixtures 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 YoeB alone, indicating that YoeB by itself does not have endoribonuclease activity under the conditions used. The 70 S ribosomes increased upon YoeB induction, and YoeB was found to be specifically associated with 50 S subunits. Using tetracycline and hygromycin B, we demonstrated that YoeB binds to the 50 S ribosomal subunit in 70 S ribosomes and interacts with the A site leading to mRNA cleavage at this site. As a result, the 3'-end portion of the mRNA was released from ribosomes, and translation initiation was effectively inhibited. These results demonstrate that YoeB primarily inhibits translation initiation.
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: Masayori
authors.initials: M
authors.lastname: Inouye
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001427:Bacterial Toxins / Q000737:chemistry / Q000378:metabolism*; D002474:Cell-Free System / Q000737:chemistry / Q000378:metabolism; D018387:Codon, Initiator / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D006921:Hygromycin B / Q000494:pharmacology; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000737:chemistry / Q000378:metabolism*; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000737:chemistry / Q000378:metabolism; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry / Q000378:metabolism; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001427:Bacterial Toxins; D018387:Codon, Initiator; D029968:Escherichia coli Proteins; D011500:Protein Synthesis Inhibitors; D012329:RNA, Bacterial; D012346:RNA, Transfer, Amino Acyl; D012358:RNA, Transfer, Met; C484519:YefM protein, E coli; C504245:YoeB protein, E coli; D006921:Hygromycin B; D013752:Tetracycline