Myricetin Preferentially Binds to Interfacial Regions in Domains 1 – 3 to Inhibit Cholesterol-Dependent Cytolysins: A Molecular Docking Study

Cholesterol-dependent cytolysins (CDCs) are proteinaceous toxins secreted as monomers by some Gram-positive and Gram-negative bacteria that contribute to their pathogenicity. These toxins bind to either cholesterol or human CD59, leading to massive structural changes, toxin oligomerization, formation of very large pores, and ultimately cell death, making these proteins promising targets for inhibition. Myricetin, and its related flavonoids, have been previously identified as a candidate small molecule inhibitor of specific CDCs such as listeriolysin O (LLO) and suilysin (SLY), interfering with their oligomerization. In this work, molecular docking was performed to assess the interaction of myricetin with other CDCs whose crystal structures are already known. Results indicated that although myricetin bound to the hitherto identified cavity in domain 4 (D4), much more efficient and stable binding was obtained in sites along the interfacial regions of domains 1 – 3 (D1 – D3). This was common among the tested CDCs, which was primarily due to much more extensive stabilizing intermolecular interactions, as indicated by post-docking analysis. Specifically, myricetin bound to (1) the interface of the three domains in anthrolysin O (ALO), perfringolysin O (PFO), pneumolysin (PLY), SLY, and vaginolysin (VLY), (2) at/near the D1/D3 interface in LLO and streptolysin O (SLO), and (3) along the D2/D3 interface in intermedilysin (ILY). These findings provide theoretical basis on the possibility of using myricetin and its related compounds as a broad-spectrum inhibitor of CDCs to potentially address the diseases associated with these pathogens.