- PDB-6g1c: Crystal structure of the N-terminal domain of Burkholderia Pseudo... -
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Basic information
Entry
Database: PDB / ID: 6g1c
Title
Crystal structure of the N-terminal domain of Burkholderia Pseudomallei antitoxin HicB
Components
Antitoxin HicB
Keywords
ANTITOXIN / N-terminal domain of the antitoxin HicB which acts as an inhibitor to HicA
Function / homology
HicB-like antitoxin of toxin-antitoxin system / HicB_like antitoxin of bacterial toxin-antitoxin system / TTHA1013/TTHA0281-like / HicB-like antitoxin of toxin-antitoxin system domain-containing protein
Biotechnology and Biological Sciences Research Council
BB/J014400/1
United Kingdom
Citation
Journal: J Biol Chem / Year: 2018 Title: The molecular basis of protein toxin HicA-dependent binding of the protein antitoxin HicB to DNA. Authors: Ashley J Winter / Christopher Williams / Michail N Isupov / Hannah Crocker / Mariya Gromova / Philip Marsh / Oliver J Wilkinson / Mark S Dillingham / Nicholas J Harmer / Richard W Titball / Matthew P Crump / Abstract: Toxin-antitoxin (TA) systems are present in many bacteria and play important roles in bacterial growth, physiology, and pathogenicity. Those that are best studied are the type II TA systems, in which ...Toxin-antitoxin (TA) systems are present in many bacteria and play important roles in bacterial growth, physiology, and pathogenicity. Those that are best studied are the type II TA systems, in which both toxins and antitoxins are proteins. The HicAB system is one of the prototypic TA systems, found in many bacterial species. Complex interactions between the protein toxin (HicA), the protein antitoxin (HicB), and the DNA upstream of the encoding genes regulate the activity of this system, but few structural details are available about how HicA destabilizes the HicB-DNA complex. Here, we determined the X-ray structures of HicB and the HicAB complex to 1.8 and 2.5 Å resolution, respectively, and characterized their DNA interactions. This revealed that HicB forms a tetramer and HicA and HicB form a heterooctameric complex that involves structural reorganization of the C-terminal (DNA-binding) region of HicB. Our observations indicated that HicA has a profound impact on binding of HicB to DNA sequences upstream of in a stoichiometric-dependent way. At low ratios of HicA:HicB, there was no effect on DNA binding, but at higher ratios, the affinity for DNA declined cooperatively, driving dissociation of the HicA:HicB:DNA complex. These results reveal the structural mechanisms by which HicA de-represses the HicB-DNA complex.
Evidence: gel filtration, Gel filtration resulted in a dimer, mass spectrometry, Native mass spectrometry showed existance of a dimer state in the gas phase