Fig. 1. Structures of the [Fe:S] clusters of NifD₂K₂ of A. vinelandii. (A) FeMo-co in DT-reduced NifD₂K₂ (PDB ID: 3U7Q); (B) P-cluster in the resting all-ferrous P^N state (PDB ID: 3MIN); (C) P-cluster in the 2-electron oxidized P²⁺ state (PDB ID: 2MIN).¹⁵.