4Q3A:
reference: The Formation of Pyrroline and Tetrahydropyridine Rings in Amino Acids Catalyzed by Pyrrolysine Synthase (PylD)., Quitterer F, Beck P, Bacher A, Groll M, Angew Chem Int Ed Engl. 2014 Jun 10. doi: 10.1002/anie.201402595. PMID: 24916332

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