Inhibitory effect of theaflavin-3,3'-digallate can involve its binding to the "stem" domain of α-hemolysin of Staphylococcus aureus

Infections caused by Staphylococcus aureus are currently a worldwide threat affecting millions of in-dividuals. The pathogenicity of S. aureus is associated with numerous virulence factors, including cell surface proteins, polysaccharides, and secreted toxins. The pore-forming alpha-hemolysin, known as alpha-toxin, is produced by nearly all virulent strains of S. aureus and is implicated in several diseases including skin and soft tissue infections, atopic dermatitis, and pneumonia. There are currently no vaccines available for the prevention of S. aureus infections and the efficacy of available antibiotics has been fading. In this study we examined the mode of antihemolytic activity of theaflavin-3,3'-digallate against alpha-hemolysin of methicillin-resistant S. aureus by molecular docking using AutoDock Vina as the molecular docking tool. The theaflavin-3,3'-digallate docked the molecular sequence of the Hla (PDB ID:7ahl). The scores of the top 10 binding modes obtained were between -9.0 and -8.5 kcal mol-1, and the best binding mode was -9.0 kcal mol-1. Direct binding sites of theaflavin-3,3'- digallate to the "stem" domain of Hla were revealed which primarily targeted of the residues Met113, Thr117, Asn139. The disclosure of this potential binding mode warrants further clinical evaluation of theaflavin-3,3'-digallate as an anti-hemolytic compound in order to practically validate our results.