For example SARS-CoV-2 Mpro bound to 13b PDB:6Y2F One protomer of the dimer is shown in light blue, the other one in orange. Domains are labeled by Roman numerals. Amino acid residues of the catalytic site are indicated as yellow spheres for Cys145 and blue spheres for His41. Asterisks mark residues from protomer B (orange). Black spheres indicate the positions of Ala285 for each of the two domains III. Chain termini are labeled N and C for molecule A (light blue) and N* and C* for molecule B (orange). doi:10.1126/science.abb3405