3KWA:
reference: Polyamines Inhibit Carbonic Anhydrases by Anchoring to the Zinc-Coordinated Water Molecule., Carta F, Temperini C, Innocenti A, Scozzafava A, Kaila K, Supuran CT, J Med Chem. 2010 Jun 30. PMID: 20590092

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