Probing the Highly Disparate Dual Inhibitory Mechanisms of Novel Quinazoline Derivatives Against Protein Kinases A and B

() serine/threonine (Ser/Thr) Protein kinases A (PknA) and B (PknB) have been identified as highly attractive targets for overcoming drug resistant tuberculosis. A recent lead series optimization study yielded compound which exhibited potencies ~1000 times higher than compound . This huge discrepancy left us curious to investigate the mechanistic 'dual' (in)activities of the compound using computational methods, as carried out in this study. Findings revealed that stabilized the PknA and B conformations and reduced their structural activities relative to . Optimal stability of in the hydrophobic pockets further induced systemic alterations at the P-loops, catalytic loops, helix Cs and DFG motifs of PknA and B. Comparatively, was more surface-bound with highly unstable motions. Furthermore, demonstrated similar binding patterns in PknA and B, involving conserved residues of their binding pockets. Both π and hydrogen interactions played crucial roles in the binding of , which altogether culminated in high Δ for both proteins. On the contrary, the binding of was characterized by unfavorable interactions with possible repulsive effects on its optimal dual binding to both proteins, as evidenced by the relatively lowered Δ. These findings would significantly contribute to the rational structure-based design of novel and highly selective dual inhibitors of PknA and B.