5C4I:
reference: The Structure of an Oxalate Oxidoreductase Provides Insight into Microbial 2-Oxoacid Metabolism., Gibson MI, Brignole EJ, Pierce E, Can M, Ragsdale SW, Drennan CL, Biochemistry. 2015 Jun 24. PMID: 26061898

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