1AKK:
reference: Solution structure of oxidized horse heart cytochrome c., Banci L, Bertini I, Gray HB, Luchinat C, Reddig T, Rosato A, Turano P, Biochemistry 1997 Aug 12;36(32):9867-77. PMID: 9245419

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