2CFM:
reference: The closed structure of an archaeal DNA ligase from Pyrococcus furiosus., Nishida H, Kiyonari S, Ishino Y, Morikawa K, J Mol Biol. 2006 Jul 28;360(5):956-67. Epub 2006 Jun 12. PMID: 16820169

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