6hpb | pdb_00006hpb
Crystal structure of the E.coli HicAB toxin-antitoxin complex
Structural highlights
FunctionHICA_ECOLI Toxic component of a type II toxin-antitoxin (TA) system. A probable translation-independent mRNA interferase. Overexpression causes cessation of cell growth and inhibits cell proliferation via inhibition of translation; this blockage is overcome (after 90 minutes) by subsequent expression of antitoxin HicB. Overexpression causes cleavage of a number of mRNAs and tmRNA, in a translation-independent fashion, suggesting this is an mRNA interferase (PubMed:19060138). mRNA interferases play a role in bacterial persistence to antibiotics (PubMed:21788497).[1] [2] Publication Abstract from PubMedThe 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. The E. coli HicB Antitoxin Contains a Structurally Stable Helix-Turn-Helix DNA Binding Domain.,Manav MC, Turnbull KJ, Jurenas D, Garcia-Pino A, Gerdes K, Brodersen DE Structure. 2019 Sep 4. pii: S0969-2126(19)30279-5. doi:, 10.1016/j.str.2019.08.008. PMID:31495532[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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