5I14:
reference: Metal ions-binding T4 lysozyme as an intramolecular protein purification tag compatible with X-ray crystallography., Boura E, Baumlova A, Chalupska D, Dubankova A, Klima M, Protein Sci. 2017 Jun;26(6):1116-1123. doi: 10.1002/pro.3162. Epub 2017 Apr 2. PMID: 28342173

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