2CA4:
reference: Molecular basis for enzymatic sulfite oxidation: how three conserved active site residues shape enzyme activity., Bailey S, Rapson T, Johnson-Winters K, Astashkin AV, Enemark JH, Kappler U, J Biol Chem. 2009 Jan 23;284(4):2053-63. Epub 2008 Nov 12. PMID: 19004819

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