2B4Z:
reference: High resolution X-ray crystallographic structure of bovine heart cytochrome c and its application to the design of an electron transfer biosensor., Mirkin N, Jaconcic J, Stojanoff V, Moreno A, Proteins. 2008 Jan 1;70(1):83-92. PMID: 17634981

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