4HEH:
reference: Redox and Light Control the Heme-Sensing Activity of AppA., Yin L, Dragnea V, Feldman G, Hammad LA, Karty JA, Dann CE 3rd, Bauer CE, MBio. 2013 Aug 27;4(5). pii: e00563-13. doi: 10.1128/mBio.00563-13. PMID: 23982072

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