_EC 1.18.6.- With dinitrogen as acceptor. 39 PDB entries  
EC 1.-.-.- Oxidoreductases. [9,191 PDB entries]
EC 1.18.-.- Acting on iron-sulfur proteins as donors. [126 PDB entries]
EC 1.18.6.- With dinitrogen as acceptor. [39 PDB entries]    
EC 1.18.6.1 Nitrogenase. [39 PDB entries]