2WSH:
reference: Structure of Bacteriophage T4 Endonuclease II Mutant E118A, a Tetrameric GIY-YIG Enzyme., Andersson CE, Lagerback P, Carlson K, J Mol Biol. 2010 Feb 13. PMID: 20156453

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