2CBE:
reference: Structure of native and apo carbonic anhydrase II and structure of some of its anion-ligand complexes., Hakansson K, Carlsson M, Svensson LA, Liljas A, J Mol Biol 1992 Oct 20;227(4):1192-204. PMID: 1433293

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