Structure of Porcine deltacoronavirus (PDCoV) main protease (Mpro). (A) Overall structure of the PDCoV Mpro-N3 complex. The two protomers, A and B, are colored violet and deep teal, respectively; the substrate-binding pocket is indicated by dashed lines; inhibitor N3 is shown as green sticks; and the catalytic dyads Cys-144 and His-41 are colored yellow. (B) Superposition of a representative CoV Mpro from each of four genera: Deltacoronavirus (PDCoV, deep teal) and three other genera (human coronavirus NL63 [HCoV-NL63], human coronavirus 229E [HCoV-229E], porcine epidemic diarrhea virus [PEDV], feline infectious peritonitis virus [FIPV], transmissible gastroenteritis virus [TGEV], severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], severe acute respiratory syndrome coronavirus [SARS-CoV], Middle East respiratory syndrome coronavirus [MERS-CoV], human coronavirus HKU1 [HCoV-HKU1], mouse hepatitis virus A59 [MHV-A59] and infectious bronchitis virus [IBV], silver).