Like other protein-binding CoVs, except for MHV binding to the protein receptor CEACAM1 via S1-NTD [250] (Table 2), MERS-CoV binds to the outer surface of DDP4 via S1B (S1-CTD) and it does not bind to the DDP4 catalytic pocket and does not require DDP4 catalytic activity (Figure 4b) [251].