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The molecular basis of protein toxin HicA–dependent binding of the protein antitoxin HicB to DNA

DOI: 10.1074/jbc.RA118.005173 DOI Help

Authors: Ashley J. Winter (University of Bristol) , Christopher Williams (University of Bristol) , Michail N. Isupov (University of Exeter) , Hannah Crocker (University of Bristol) , Mariya Gromova (University of Bristol) , Philip Marsh (University of Bristol) , Oliver J. Wilkinson (University of Bristol) , Mark S. Dillingham (University of Bristol) , Nicholas J. Harmer (University of Exeter) , Richard W. Titball (University of Exeter) , Matthew P. Crump (University of Bristol)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry

State: Published (Approved)
Published: October 2018
Diamond Proposal Number(s): 12342

Open Access Open Access

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 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 hetero-octameric 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 hicAB 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.

Journal Keywords: toxin-antitoxin system; Persistence; conditional cooperativity; HicAB; type II TA system; structural biology; DNA binding protein; protein-protein interaction; bacterial toxin; antibiotic resistance; X-ray crystallography

Diamond Keywords: Bacteria

Subject Areas: Biology and Bio-materials

Instruments: B21-High Throughput SAXS , I03-Macromolecular Crystallography , I04-Macromolecular Crystallography

Added On: 25/10/2018 14:44


Discipline Tags:

Life Sciences & Biotech Health & Wellbeing Antibiotic Resistance Infectious Diseases Pathogens Structural biology

Technical Tags:

Diffraction Scattering Macromolecular Crystallography (MX) Small Angle X-ray Scattering (SAXS)