1HKX:
reference: Crystal structure of a tetradecameric assembly of the association domain of Ca2+/calmodulin-dependent kinase II., Hoelz A, Nairn AC, Kuriyan J, Mol Cell 2003 May;11(5):1241-51. PMID: 12769848

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