Targeting Bacterial\nSortase A with Covalent Inhibitors: 27 New Starting Points for Structure-Based\nHit-to-Lead Optimization

Because of its essential role as a bacterial virulence\nfactor, enzyme sortase A (SrtA) has become an attractive target for\nthe development of new antivirulence drugs against Gram-positive infections.\nHere we describe 27 compounds identified as covalent inhibitors of Staphylococcus aureus SrtA by screening a library of approximately\n50 000 compounds using a FRET assay followed by NMR-based validation\nand binding reversibility analysis. Nineteen of these compounds displayed\nonly moderate to weak cytotoxicity, with CC50 against NIH\n3T3 mice fibroblast cells ranging from 12 to 740 μM. Analysis\nusing covalent docking suggests that the inhibitors initially associate\nvia hydrophobic interactions, followed by covalent bond formation\nbetween the SrtA active site cysteine and an electrophilic center\nof the inhibitor. The compounds represent good starting points that\nhave the potential to be developed into broad spectrum antivirulence\nagents as exemplified by hit-to-lead optimization of one of the compounds.