Characterisation of Staphylococcus aureus virulence factor EsxA and structure-based screening of EsxA inhibitors for combating methicillin-resistant S aureus: abridged secondary publication
KH Sze, RYT Kao
Department of Microbiology, The University of Hong Kong, Hong Kong
1. EsxB did not interact with EsxA by cell-free assays (ITC and NMR titration) and cell-based assays (coIP and pull-down).
2. Pull-down and NMR titration assays showed that EsxA was interacting with lipid mediators HOTrE and sphingosylphosphorylcholine, respectively. These results suggested that EsxA may function as a lipid mediator binding protein, and that EsxA is an immune evasion gene and provide important clue to delineate its mechanism of immune evasion.
3. A high performance platform was established for in silico structure-based screening against pathogen targets. The EsxA X-ray structure was subjected to structure-based screening with a ligand library containing 6.8 million lead-like or active lead ligands.
4. Of the 100 highest-scoring compounds, five were validated by the secondary NMR titration screen. One hit compound (6058448) showed MIC at 25 μM level by broth microdilution test, and another hit compound (5674203) also showed antivirulence effects by inhibiting the expression of both protein A and alpha-toxin of US300 strain.