2QOJ:
reference: Coevolution of a homing endonuclease and its host target sequence., Scalley-Kim M, McConnell-Smith A, Stoddard BL, J Mol Biol. 2007 Oct 5;372(5):1305-19. Epub 2007 Aug 2. PMID: 17720189

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