6NIR:
reference: GII.4 Norovirus Protease Shows pH-Sensitive Proteolysis with a Unique Arg-His Pairing in the Catalytic Site., Viskovska MA, Zhao B, Shanker S, Choi JM, Deng L, Song Y, Palzkill T, Hu L, Estes MK, Venkataram Prasad BV, J Virol. 2019 Mar 5;93(6). pii: JVI.01479-18. doi: 10.1128/JVI.01479-18. Print, 2019 Mar 15. PMID: 30626675

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