3CCX:
reference: Altering substrate specificity at the heme edge of cytochrome c peroxidase., Wilcox SK, Jensen GM, Fitzgerald MM, McRee DE, Goodin DB, Biochemistry 1996 Apr 16;35(15):4858-66. PMID: 8664277

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