5j9i
Crystal structure of the HigA2 antitoxin C-terminal domain
Structural highlights
FunctionHIGA2_VIBCH Antitoxin component of a toxin-antitoxin (TA) module that counteracts the effect of the HigB-2 toxin. Binds to its own promoter and regulates transcription of the higB-2/higA-2 operon.[1] Publication Abstract from PubMedToxin-antitoxin (TA) modules are small operons involved in bacterial stress response and persistence. higBA operons form a family of TA modules with an inverted gene organization and a toxin belonging to the RelE/ParE superfamily. Here, we present the crystal structures of chromosomally encoded Vibrio cholerae antitoxin (VcHigA2), toxin (VcHigB2) and their complex, which show significant differences in structure and mechanisms of function compared to the higBA module from plasmid Rts1, the defining member of the family. The VcHigB2 is more closely related to Escherichia coli RelE both in terms of overall structure and the organization of its active site. VcHigB2 is neutralized by VcHigA2, a modular protein with an N-terminal intrinsically disordered toxin-neutralizing segment followed by a C-terminal helix-turn-helix dimerization and DNA binding domain. VcHigA2 binds VcHigB2 with picomolar affinity, which is mainly a consequence of entropically favorable de-solvation of a large hydrophobic binding interface and enthalpically favorable folding of the N-terminal domain into an alpha-helix followed by a beta-strand. This interaction displaces helix alpha3 of VcHigB2 and at the same time induces a one-residue shift in the register of beta-strand beta3, thereby flipping the catalytically important Arg64 out of the active site. Ribosome-dependent Vibrio cholerae mRNAse HigB2 is regulated by a beta-strand sliding mechanism.,Hadzi S, Garcia-Pino A, Haesaerts S, Jurenas D, Gerdes K, Lah J, Loris R Nucleic Acids Res. 2017 Feb 28. doi: 10.1093/nar/gkx138. PMID:28334932[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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