5U6Y:
reference: The CaMKII holoenzyme structure in activation-competent conformations., Myers JB, Zaegel V, Coultrap SJ, Miller AP, Bayer KU, Reichow SL, Nat Commun. 2017 Jun 7;8:15742. doi: 10.1038/ncomms15742. PMID: 28589927

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