1QLE:
reference: The cytochrome c oxidase from Paracoccus denitrificans does not change the metal center ligation upon reduction., Harrenga A, Michel H, J Biol Chem 1999 Nov 19;274(47):33296-9. PMID: 10559205

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