4OTT:
reference: Low resolution X-ray structure of gamma-glutamyltranspeptidase from Bacillus licheniformis: Opened active site cleft and a cluster of acid residues potentially involved in the recognition of a metal ion., Lin LL, Chen YY, Chi MC, Merlino A, Biochim Biophys Acta. 2014 Apr 26;1844(9):1523-1529. doi:, 10.1016/j.bbapap.2014.04.016. PMID: 24780583

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