Summary of the MM-GBSA calculations of binding free energy of ATP (ΔGbind) based on the proposed ATP-binding modes.

#the PDB entry codes for closed and open structures used in in silico docking are 3H9V and 4WD1, respectively;aDocking ATP into closed or open structures of zfP2X4.1 with proper preparation and minimization beforehand through a rigid body docking strategy;bDocking ATP into closed structure of zfP2X4.1 that has been previously sampled and averaged using 2-ns MD simulations through a rigid body docking strategy;&ΔGbind-Coulomb, ΔGbind-vdW, ΔGbind-Solv represents contribution of Coulomb energy, van der Waals energy and Generalized Born electrostatic solvation energy in ΔGbind calculation, respectively. An estimate of strain energies for the ligand and the receptor were also shown in summary.n.d., the ΔGbind value of AR2 was not measured for there is no AR2 pose observed in in silico docking.