2NQO:
reference: Autoprocessing of Helicobacter pylori gamma-glutamyltranspeptidase leads to the formation of a threonine-threonine catalytic dyad., Boanca G, Sand A, Okada T, Suzuki H, Kumagai H, Fukuyama K, Barycki JJ, J Biol Chem. 2007 Jan 5;282(1):534-41. Epub 2006 Nov 15. PMID: 17107958

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