Insight into the Dual Inhibition Mechanism of Corilagin against MRSA Serine/Threonine Phosphatase (Stp1) by Molecular Modeling

Serine/threonine phosphatase (Stp1) is known to be involved in the regulation of cysteine phosphorylation levels in many different pathways, such as virulence factor regulation in methicillin-resistant Staphylococcus aureus (MRSA). Therefore, Stp1 can be used as a potential target for inhibiting MRSA infection. In this study, using virtual screening, we found that corilagin, a natural compound, was screened as a potential Stp1 inhibitor. Then, the phosphatase assay exhibited high inhibitory activity against Stp1. On the basis of the enzyme kinetics experiment, we found that corilagin exhibited a dual inhibitory mechanism of competitive and allosteric inhibition. To further elucidate the mechanism of interaction between corilagin and Stp1, molecular dynamics (MD) simulations were performed on the Stp1-corilagin complex. Consistent with the mutagenesis assays and fluorescence quenching assays results, the competitive and allosteric binding sites of corilagin with Stp1 were identified. In the competitive binding site of Stp1, Asn162, Ile164, Tyr199, and Lys232 were found to play a key role in this complex. In the allosteric binding site, hydrophobic interaction was the main binding force. The Asn142, Val145, Leu146, Pro152, and Phe179 residues of Stp1 were found to play a critical role in the binding of corilagin with Stp1. In this study, we used MD simulation to reveal the ligand-protein interactions, providing a theoretical basis. This research work, thus, lays down the foundation for the development of new Stp1 inhibitors to be utilized in the future.