1BVB:
reference: Heme packing motifs revealed by the crystal structure of the tetra-heme cytochrome c554 from Nitrosomonas europaea., Iverson TM, Arciero DM, Hsu BT, Logan MS, Hooper AB, Rees DC, Nat Struct Biol 1998 Nov;5(11):1005-12. PMID: 9808046

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