Molecular docking was performed using HDOCK server (http://hdock.phys.hust.edu.cn/), which calculates protein-protein interaction through a hybrid algorithm of template-based and template-free docking. The crystal structure of S protein receptor binding domain (RBD) (PDB ID: 6M0J), corresponding to the residues 437–508 of S protein, was docked against the homology models of bat ACE2 [27]. The calculation was carried out imposing as constraints 8 Å distance between S protein A475 and ACE2 E23 and 5 Å distance between S protein N501 and ACE2 D355. The results were analyzed according to i) docking score value (kcal/mol), generated by HDOCK scoring function [28]; ii) ligand root-mean-square deviation (RMSD) of atomic positions value (Å). RMSD measures the distance between the docked pose and a model of the same ligand predicted by template-based homology modelling generated by HDOCK (the lower the value, the more similar the poses).