3DR2:
reference: The first crystal structure of gluconolactonase important in the glucose secondary metabolic pathways., Chen CN, Chin KH, Wang AH, Chou SH, J Mol Biol. 2008 Dec 19;384(3):604-14. Epub 2008 Sep 30. PMID: 18848569

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