4BMW:
reference: Iron Binding at Specific Sites within the Octameric HbpS Protects Streptomycetes from Iron-Mediated Oxidative Stress., Wedderhoff I, Kursula I, Groves MR, Ortiz de Orue Lucana D, PLoS One. 2013 Aug 27;8(8):e71579. doi: 10.1371/journal.pone.0071579. PMID: 24013686

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