Figure 3: Structural comparison of CTDs of different β-CoV S proteins.

The core subdomains are blue, and the insertion loops are magenta. (a) HKU1 CTD; (b) MHV CTD (PDB: 3JCL); (c) (PDB: 2AJF); (d) MERS-CoV RBD (PDB: 4L72); (e) HKU4 RBD (PDB: 4QZV) and (f) HKU9 RBD (PDB: 5GYQ).