6BTX:
reference: Calcium is an essential cofactor for metal efflux by the ferroportin transporter family., Deshpande CN, Ruwe TA, Shawki A, Xin V, Vieth KR, Valore EV, Qiao B, Ganz T, Nemeth E, Mackenzie B, Jormakka M, Nat Commun. 2018 Aug 6;9(1):3075. doi: 10.1038/s41467-018-05446-4. PMID: 30082682

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