3KGV:
reference: Crystal structure of DNA-PKcs reveals a large open-ring cradle comprised of HEAT repeats., Sibanda BL, Chirgadze DY, Blundell TL, Nature. 2010 Jan 7;463(7277):118-21. Epub 2009 Dec 20. PMID: 20023628

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