1A8K:
reference: Crystallographic analysis of human immunodeficiency virus 1 protease with an analog of the conserved CA-p2 substrate -- interactions with frequently occurring glutamic acid residue at P2' position of substrates., Weber IT, Wu J, Adomat J, Harrison RW, Kimmel AR, Wondrak EM, Louis JM, Eur J Biochem 1997 Oct 15;249(2):523-30. PMID: 9370363

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