4FAS:
reference: Structural Studies of Hydroxylamine Oxidoreductase Reveal a Unique Heme Cofactor and a Previously Unidentified Interaction Partner., Cedervall P, Hooper AB, Wilmot CM, Biochemistry. 2013 Aug 26. PMID: 23952581

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