Binding mechanism of anacardic acid, carnosol and garcinol with PCAF: A comprehensive study using molecular docking and molecular dynamics simulations and binding free energy analysis

The p300/CBP associated factor bromodomain (PCAF Brd) is emerged as one of the promising target proteins for different types of cancers. PCAF is one among the histone acetyltransferase enzymes which involved in the regulation of transcriptase process by modifying the chromatin structure. Anacardic acid, carnosol, garcinol are the experimentally reported inhibitors of PCAF Brd; however, their detailed binding mechanism these inhibitors are not yet known. The intermolecular interaction, binding energy, and the stability of these inhibitors with the active site of PCAF Brd are playing the key role in the binding of these inhibitors with PCAF. The in silico study incorporates the molecular docking and dynamics simulations; these molecular level simulations allow to understand the binding mechanism. In the present study, the induced fit molecular docking and molecular dynamics of anacardic acid, carnosol and garcinol molecules against the PCAF Brd have been performed. The docking score values of these molecules are -5.112 (anacardic acid), -5.141 (carnosol), -5.199 (garcinol) and -3.641 (L45) kcal/mol, respectively. Further, the molecular dynamics simulation was carried out for these docked complexes to understand their conformational their stability and binding energy from the roots means square deviation (RMSD) and root means square of fluctuation (RMSF), and molecular mechanics with the generalized born and surface area solvation (MM/GBSA) binding free energy calculations. The intermolecular interactions and binding free energy values confirm that garcinol forms key interactions and has high binding affinity towards PCAF Brd on compare with the other two inhibitors. Therefore, garcinol may be considered as a potential inhibitor of PCAF Brd.