2GIW:
reference: Solution structure of reduced horse heart cytochrome c., Banci L, Bertini I, Huber JG, Spyroulias GA, Turano P, J Biol Inorg Chem 1999 Feb;4(1):21-31. PMID: 10499099

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