Fig. 4.

The structural comparison of RBD bound with receptor and RBD subdomains in the three coronaviruses. (a) Overall structure of RBD bound with DPP4 (PDB ID: 4KR0), and (b) schematic illustration topology of the core structure and RBM in the MERS-CoV RBD. (c) Overall structure of RBD bound with ACE2 (PDB ID: 2AJF), and (d) schematic illustration topology of the core structure and RBM in the SARS-CoV RBD. (e) Overall structure of RBD bound with ACE2 (PDB ID: 6M0J), and (f) schematic illustration topology of the core structure and RBM in the SARS-CoV-2 RBD. β strands are drawn as arrows and α helices are drawn as cylinders. The disulfide bonds are drawn as yellow sticks. The core subdomain is colored in green and the receptor-binding subdomain is colored in red.