3FD2:
reference: Generation of single-chain LAGLIDADG homing endonucleases from native homodimeric precursor proteins., Li H, Pellenz S, Ulge U, Stoddard BL, Monnat RJ Jr, Nucleic Acids Res. 2009 Apr;37(5):1650-62. Epub 2009 Jan 19. PMID: 19153140

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