4USJ:
reference: A widespread glutamine-sensing mechanism in the plant kingdom., Chellamuthu VR, Ermilova E, Lapina T, Luddecke J, Minaeva E, Herrmann C, Hartmann MD, Forchhammer K, Cell. 2014 Nov 20;159(5):1188-99. doi: 10.1016/j.cell.2014.10.015. PMID: 25416954

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