1N3F:
reference: Flexible DNA target site recognition by divergent homing endonuclease isoschizomers I-CreI and I-MsoI., Chevalier B, Turmel M, Lemieux C, Monnat RJ Jr, Stoddard BL, J Mol Biol 2003 May 30;329(2):253-69. PMID: 12758074

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