Resolved  crystal structures demonstrate that DPP4-recognized receptor-binding domain is localized to the S1 C-terminal portion of S protein  of MERS-CoV. The receptor-binding domain of MERS-CoV consist of ∼240 residues, spanning amino acid 367-606, which fold into a structure consisting of two subdomains, the core subdomain and the external subdomain. The core subdomain of MERS-CoV receptor-binding domain is structurally similar to that of the SARS-CoV receptor-binding domain, but the external binding subdomain is different to that of the SARS-CoV.