Fig. 2.

Complex of the nitrogenase proteins stabilized by ADP-AIF₄⁻. (Left) ADP-AlF₄⁻-stabilized half-complex between a Fe-protein dimer and an αβ-subunit pair of the MoFe protein. The subunits are depicted as Cα traces with the MoFe α- and β-subunits colored red and blue, respectively, and the individual subunits of each Fe protein colored green and yellow. Non-protein groups are shown in a space-filling representation using the color scheme of Fig. 1, with fluorine and magnesium colored orange and green, respectively. (Right) Transduction pathway coupling the nucleotide and cofactor sites in the nitrogenase complex. This view represents a slice through the complex that includes the ADP-AlF₄⁻, [4Fe:4S]-cluster, P-cluster, and FeMo-cofactor sites. The side chains of Asp-129 of each Fe-protein subunit are depicted as space-filling models to illustrate the locations of these critical residues adjacent to both the nucleotide and cluster sites.