3V2Z:
reference: Distal pocket control of nitrite binding in myoglobin., Yi J, Thomas LM, Richter-Addo GB, Angew Chem Int Ed Engl. 2012 Apr 10;51(15):3625-7. doi: 10.1002/anie.201200010., Epub 2012 Mar 1. PMID: 22383424

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