1QDB:
reference: Structure of cytochrome c nitrite reductase., Einsle O, Messerschmidt A, Stach P, Bourenkov GP, Bartunik HD, Huber R, Kroneck PM, Nature 1999 Jul 29;400(6743):476-80. PMID: 10440380

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