1GMB:
reference: Conformational component in the coupled transfer of multiple electrons and protons in a monomeric tetraheme cytochrome., Louro RO, Bento I, Matias PM, Catarino T, Baptista AM, Soares CM, Carrondo MA, Turner DL, Xavier AV, J Biol Chem 2001 Nov 23;276(47):44044-51. PMID: 11551953

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