2AGK:
reference: Crystal structure of the yeast His6 enzyme suggests a reaction mechanism., Quevillon-Cheruel S, Leulliot N, Graille M, Blondeau K, Janin J, van Tilbeurgh H, Protein Sci. 2006 Jun;15(6):1516-21. PMID: 16731983

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