Figure 3.

Key crystal contacts of C121 crystal form

(A) The 2F_o − F_c electron density belonging to the N-terminal region of the SARS-CoV-2 main protease is contoured at the 1σ level and colored in gray. Regions of the symmetry-related molecule are colored in gray, 2F_o − F_c electron density is contoured at the 1σ level and colored in slate. H bonds are indicated by black dashed lines. Elimination of these H bonds was essential to obtain the second crystal form in the P2₁2₁2₁ space group, with a more open inhibitor binding pocket for future soaking studies of the putative main protease inhibitors.

(B) Superposition of Cα atoms of our structure (PDB: 7CWB) was performed with the Mpro structure (PDB: 6WQF). Our structure is colored in salmon, while chain A of PDB: 6WQF is colored in gray. A composite omit map of the PDB: 7CWB active site is shown blue color.