4AIV:
reference: Crystal structure of NirD, the small subunit of the nitrite reductase NirBD from Mycobacterium tuberculosis, at 2.0 A resolution., Izumi A, Schnell R, Schneider G, Proteins. 2012 Sep 10. doi: 10.1002/prot.24177. PMID: 22965870

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