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

par Manav, Melek Cemre;Turnbull, Kathryn Jane;Jurenas, Dukas ;Garcia-Pino, Abel ;Gerdes, Kenn;Brodersen, Ditlev Egeskov
Référence Structure, 27, 11, page (1675-1685.e3)
Publication Publié, 2019-11-01

Article révisé par les pairs

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Résumé :

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.