4GD3:
reference: Crystal Structure of the O(2)-Tolerant Membrane-Bound Hydrogenase 1 from Escherichia coli in Complex with Its Cognate Cytochrome b., Volbeda A, Darnault C, Parkin A, Sargent F, Armstrong FA, Fontecilla-Camps JC, Structure. 2012 Dec 19. pii: S0969-2126(12)00425-X. doi:, 10.1016/j.str.2012.11.010. PMID: 23260654

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