FIGURE 2.

Structure of the NarG-H49C (A) and NarG-H49S (B) variants in the vicinity of FS0 and the Mo-bisPGD cofactor. In addition to the FS0-coordinating residues, the position of the ⁴⁹CGVNCTG⁵⁵ segment is shown in the NarG-H49C variant (A) that is unresolved in the structure of the NarG-H49S variant (B). FS0 and Mo-bisPGD are missing in the structure of the NarG-H49S mutant. A water molecule is coordinated by the NarG-Asp²²² residue that coordinates the molybdenum atom in the NarG-H49C and wild-type enzymes. A single iron atom is coordinated by the sulfur atoms of NarG-Cys⁵⁷ and NarG-Cys⁹².