FIG 4.

Interaction between MERS-CoV spike protein and DPP4s of different mammalian species. (A) Cartoon representing the binding between human DPP4 or hamster DPP4 and the spike protein of MERS-CoV. DPP4 is depicted in white; the receptor binding domain (RBD) of the spike protein of MERS-CoV is depicted in magenta and cyan. The far right panel is obtained by clockwise rotation of the middle panel along a longitudinal axis. (B) Binding energies between spike protein of MERS-CoV and DPP4 of different species as well as humanized hamster DPP4 and hamsterized human DPP4. Red bars indicate the binding energies of known binders (human and rhesus macaque DPP4), blue bars indicate the binding energies of nonbinders (hamster, mouse, and ferret DPP4), green bars indicate the binding energies of unknown binders (dromedary camel, goat, cow, and sheep), and purple bars indicate the binding energies of the in silico mutagenized hamster and human DPP4s. The DPP4 homology models were constructed using the human DPP4 structure (PDB ID 4KR0, chain A) as a template and subjected to the binding energy calculation using an all-atom distance-dependent pairwise statistical potential, DFIRE.