FIG 2.

The structure of FIPV M^pro. (A) Overall structure of the FIPV M^pro-Zn²⁺-N3 complex in surface representation. The two protomers are colored slate and deep salmon, inhibitor N3 is shown as green sticks, and Zn²⁺ is shown as a magenta sphere. (B) Distribution of the nonconserved residues between FIPV and TGEV M^pros. The structure of FIPV M^pro is shown in cartoon representation (light orange). The nonconserved residues between FIPV M^pro and TGEV M^pro are shown as cyan spheres. The N3 molecule is shown as green sticks, and the substrate-binding pocket is colored in yellow. A zoomed view of the substrate-binding pocket is shown to the left. (C) Superimposition of the substrate-binding pocket of FIPV M^pro-Zn²⁺-N3 (light orange) with that of TGEV M^pro (pale cyan). The substrate-binding pocket of the FIPV M^pro complex is colored in yellow. The S1, S2, S4, S5, and S′ subsites are labeled. The key amino acids constituting the substrate-binding pockets of FIPV M^pro and TGEV M^pro are shown as sticks. The His41 residues specifically are marked by the dashed rectangular box.