Structural basis for the dimerization and substrate recognition specificity of porcine epidemic diarrhea virus 3C-like protease

Porcine epidemic diarrhea virus (PEDV), a member of the genus Alphacoronavirus, has caused significant damage to the Asian and American pork industries. Coronavirus 3C-like protease (3CLpro), which is involved in the processing of viral polyproteins for viral replication, is an appealing antiviral drug target. Here, we present the crystal structures of PEDV 3CLpro and a molecular complex between an inactive PEDV 3CLpro variant C144A bound to a peptide substrate. Structural characterization, mutagenesis and biochemical analysis reveal the substrate-binding pockets and the residues that comprise the active site of PEDV 3CLpro. The dimerization of PEDV 3CLpro is similar to that of other Alphacoronavirus 3CLpros but has several differences from that of SARS-CoV 3CLpro from the genus Betacoronavirus. Furthermore, the non-conserved motifs in the pockets cause different cleavage of substrate between PEDV and SARS-CoV 3CLpros, which may provide new insights into the recognition of substrates by 3CLpros in various coronavirus genera.