title: Structural insight into exosite binding and discovery of novel exosite inhibitors of botulinum neurotoxin serotype A through in silico screening.
abstract: Botulinum neurotoxin serotype A (BoNT/A) is the most lethal toxin among the Tier 1 Select Agents. Development of potent and selective small molecule inhibitors against BoNT/A zinc metalloprotease remains a challenging problem due to its exceptionally large substrate binding surface and conformational plasticity. The exosites of the catalytic domain of BoNT/A are intriguing alternative sites for small molecule intervention, but their suitability for inhibitor design remains largely unexplored. In this study, we employed two recently identified exosite inhibitors, D-chicoric acid and lomofungin, to probe the structural features of the exosites and molecular mechanisms of synergistic inhibition. The results showed that D-chicoric acid favors binding at the α-exosite, whereas lomofungin preferentially binds at the β-exosite by mimicking the substrate β-sheet binding interaction. Molecular dynamics simulations and binding interaction analysis of the exosite inhibitors with BoNT/A revealed key elements and hotspots that likely contribute to the inhibitor binding and synergistic inhibition. Finally, we performed database virtual screening for novel inhibitors of BoNT/A targeting the exosites. Hits C1 and C2 showed non-competitive inhibition and likely target the α- and β-exosites, respectively. The identified exosite inhibitors may provide novel candidates for structure-based development of therapeutics against BoNT/A intoxication.
authors: NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, MD, 20850, USA, hux61@mail.nih.gov.
authors: Xin
authors: X
authors: Hu
authors: Patricia M
authors: PM
authors: Legler
authors: Noel
authors: N
authors: Southall
authors: David J
authors: DJ
authors: Maloney
authors: Anton
authors: A
authors: Simeonov
authors: Ajit
authors: A
authors: Jadhav
mesh_terms: D001665:Binding Sites; D019274:Botulinum Toxins, Type A / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000633:toxicity; D002109:Caffeic Acids / Q000737:chemistry*; D003198:Computer Simulation; D006801:Humans; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D010619:Phenazines / Q000737:chemistry*; D011485:Protein Binding; D013329:Structure-Activity Relationship; D013386:Succinates / Q000737:chemistry*
chemical_list: D002109:Caffeic Acids; D010619:Phenazines; D013386:Succinates; C100203:lomofungin; D019274:Botulinum Toxins, Type A; C100435:chicoric acid