Figure 3.

X-ray co-crystal structures of (A) 13b-K (PDB entry: 8A4T) and (B) 13b-H (PDB entry: 8A4Q) in the substrate-binding cleft of the M^pro. The orientation of the view was rotated ∼45° in the case of (B) for clarity (see Figure S4 for the alternate orientation). The carbon atoms of the compounds are depicted in yellow and those of the protein in cyan, with the exception of the Ser1 of the other monomer (green). Blue symbols (S1 and S2) indicate the canonical binding pockets for moieties P1–P4 (red symbols) of the inhibitors. The 2F_o–F_c map carved around the inhibitor is depicted as a blue mesh (contoured at 1.0). Polar contacts are represented as red dashed lines.