2Q3K:
reference: Crystal structure of lysine sulfonamide inhibitor reveals the displacement of the conserved flap water molecule in human immunodeficiency virus type 1 protease., Nalam MN, Peeters A, Jonckers TH, Dierynck I, Schiffer CA, J Virol. 2007 Sep;81(17):9512-8. Epub 2007 Jun 27. PMID: 17596316

This OCA Structure page
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