3ZJS:
reference: Structure and Haem-Distal Site Plasticity in Methanosarcina acetivorans Protoglobin., Pesce A, Tilleman L, Donne J, Aste E, Ascenzi P, Ciaccio C, Coletta M, Moens L, Viappiani C, Dewilde S, Bolognesi M, Nardini M, PLoS One. 2013 Jun 12;8(6):e66144. doi: 10.1371/journal.pone.0066144. Print 2013. PMID: 23776624

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