2G5G:
reference: Cofacial Heme Binding is Linked to Dimerization by a Bacterial Heme Transport Protein., Chan AC, Lelj-Garolla B, I Rosell F, Pedersen KA, Mauk AG, Murphy ME, J Mol Biol. 2006 Oct 6;362(5):1108-19. Epub 2006 Aug 4. PMID: 16950397

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