2WHH:
reference: Catalytic water co-existing with a product peptide in the active site of HIV-1 protease revealed by X-ray structure analysis., Prashar V, Bihani S, Das A, Ferrer JL, Hosur M, PLoS One. 2009 Nov 17;4(11):e7860. PMID: 19924250

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).