1XRK:
reference: Engineering a selectable marker for hyperthermophiles., Brouns SJ, Wu H, Akerboom J, Turnbull AP, de Vos WM, van der Oost J, J Biol Chem 2005 Mar 25;280(12):11422-31. Epub 2005 Jan 7. PMID: 15640151

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