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The E. coli HicB Antitoxin Contains a Structurally Stable Helix-Turn-Helix DNA Binding Domain

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  • Cemre Manav
  • Kathryn Jane Turnbull, University of Copenhagen
  • ,
  • Dukas Jurėnas, Cellular and Molecular Microbiology, Université Libre de Bruxelles, Gosselies 6041, Belgium.
  • ,
  • Abel Garcia-Pino, Cellular and Molecular Microbiology, Université Libre de Bruxelles, Gosselies 6041, Belgium., Walloon Excellence in Life Sciences and Biotechnology (WELBIO)
  • ,
  • Kenn Gerdes, University of Copenhagen
  • ,
  • Ditlev Egeskov Brodersen

The E. coli hicAB type II toxin-antitoxin locus is unusual by being controlled by two promoters and by having the toxin encoded upstream of the antitoxin. HicA toxins contain a double-stranded RNA-binding fold and cleaves both mRNA and tmRNA in vivo, while HicB antitoxins contain a partial RNase H fold and either a helix-turn-helix (HTH) or ribbon-helix-helix domain. It is not known how an HTH DNA-binding domain affects higher-order structure for the HicAB modules. Here, we present crystal structures of the isolated E. coli HicB antitoxin and full-length HicAB complex showing that HicB forms a stable DNA-binding module and interacts in a canonical way with HicA despite the presence of an HTH-type DNA-binding domain. No major structural rearrangements take place upon binding of the toxin. Both structures expose well-ordered DNA-binding motifs allowing a model for DNA binding by the antitoxin to be generated.

Original languageEnglish
Pages (from-to)1675-1685.e3
Publication statusPublished - Nov 2019

    Research areas

  • DNA-binding protein, RNase H, antitoxin, helix-turn-helix, ribbon-helix-helix, toxin

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