5B66:
reference: Two Different Structures of the Oxygen-Evolving Complex in the Same Polypeptide Frameworks of Photosystem II., Tanaka A, Fukushima Y, Kamiya N, J Am Chem Soc. 2017 Jan 30. doi: 10.1021/jacs.6b09666. PMID: 28102667

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