3RTL:
reference: Unique Heme-Iron Coordination by the Hemoglobin Receptor IsdB of Staphylococcus aureus., Gaudin CF, Grigg JC, Arrieta AL, Murphy ME, Biochemistry. 2011 Jun 21;50(24):5443-5452. Epub 2011 May 26. PMID: 21574663

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