3OOR:
reference: Evolution of I-SceI Homing Endonucleases with Increased DNA Recognition Site Specificity., Joshi R, Ho KK, Tenney K, Chen JH, Golden BL, Gimble FS, J Mol Biol. 2010 Oct 26. PMID: 21029741

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