4ZUH:
reference: Structural basis for the dimerization and substrate recognition specificity of porcine epidemic diarrhea virus 3C-like protease., Ye G, Deng F, Shen Z, Luo R, Zhao L, Xiao S, Fu ZF, Peng G, Virology. 2016 Jul;494:225-35. doi: 10.1016/j.virol.2016.04.018. Epub 2016 Apr, 26. PMID: 27128350

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