Identification of potential inhibitors of sortase A: Binding studies, in-silico docking and protein-protein interaction studies of sortase A from Enterococcus faecalis

Enterococcus faecalis (Ef) is a Gram positive multidrug resistant (MDR) bacterium contributing about 70% of total enterococcal infections. In Ef, a membrane anchored transpeptidase Sortase A plays a major role in biofilm formation. Therefore, it has been recognized as an ideal drug target against Ef. In this regard to identify the potential inhibitors of Ef Sortase A (EfSrtA∆59), we have cloned, expressed and purified EfSrtA∆59. We have also done the in-silico docking studies to identify lead molecules interacting with EfSrtA∆59. Furthermore, the binding studies of these identified lead molecules were performed with EfSrtA∆59 using fluorescence and CD spectroscopic studies. We also identified the interaction partner of EfSrtA∆59 using STRING. Protein-protein docking studies were also performed. Docking experiment revealed that benzylpenicillin, cefotaxime, pantoprazole and valsartan were bound to same site on the protein with similar interactions. Binding studies using fluorescence spectroscopic studies confirmed the binding of all the ligands to EfSrtA∆59, which was further validated by far and near-UV CD experiments. Thermo stability experiments validate the stability-activity trade-off hypothesis. Sequence based interaction studies identified that EfSrtA∆59 interact with the Ef_1091, Ef_1093 and Ef_2658 proteins. Homology model of Ef_1091 and Ef_1093 was docked with modeled EfSrtA∆59 and their interactions are also discussed.