Deciphering the binding mode of Zolpidem to GABA _A α ₁ receptor - Insights from molecular dynamics simulation

To investigate the binding mode of Zolpidem to GABA _A and to delineate the conformational changes induced upon agonist binding, we carried out atomistic molecular dynamics simulation using the ligand binding domain of GABA _A α ₁ receptor. Comparative molecular dynamics simulation of the apo and the holo form of GABA _A receptor revealed that γ ₂/α ₁ interface housing the benzodiazepine binding site undergoes distinct conformational changes upon Zolpidem binding. We notice that C loop of the α ₁ subunit experiences an inward motion toward the vestibule and the F loop of γ ₂ sways away from the vestibule, an observation that rationalizes Zolpidem as an alpha1 selective agonist. Energy decomposition analysis carried out was able to highlight the important residues implicated in Zolpidem binding, which were largely in congruence with the experimental data. The simulation study disclosed herein provides a meaningful insight into Zolpidem-GABA _AR interactions and helps to arrive at a binding mode hypothesis with implications for drug design.