1FNN:
reference: Structure and function of Cdc6/Cdc18: implications for origin recognition and checkpoint control., Liu J, Smith CL, DeRyckere D, DeAngelis K, Martin GS, Berger JM, Mol Cell 2000 Sep;6(3):637-48. PMID: 11030343

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