Figure 3.

Interactions between Fld and the Fe protein analyzed in silico docking models suggest more complementary docking between the MgADP-bound Fe protein and Fld. A, the docking model between the MgADP-bound Fe protein (light blue, PDB code 1FP6) and Fld (violet, PDB code 1YOB) displays a distance of 6.4 Å between the [4Fe-4S] cluster and the FMN cofactor measured in PyMOL. B, a distance of 9.4 Å between the [4Fe-4S] cluster and the FMN cofactor was measured in PyMOL for the docking model between the Fe protein from the nitrogenase complexes (tan, PDB code 4WZB) and Fld (violet, PDB code 1YOB). C, interactions for the docking model between the MgADP-bound Fe protein basic amino acid residues Arg¹⁰⁰ and Arg¹⁴⁰ and docked Fld acidic residues Glu¹⁰⁴, Asp¹⁵⁴, and Glu⁵⁹. D, interactions between Arg¹⁰⁰ of the Fe protein from the MgAMPPCP-stabilized nitrogenase complex and docked Fld acidic residues Glu⁶¹, Asp⁶⁸, and Glu⁷⁰. Arg¹⁴⁰ is positioned so that it can no longer form salt bridge interactions with any Fld acidic residues.