FIGURE 3.

Unresolved residues in the NarG-H49S mutant. Residues comprising NarG-Ser⁴⁹ to NarG-Gly⁵⁵ are not observed in the NarG-H49S mutant. The location of these residues in the NarG-H49C mutant is shown in dark gray. The carbonyl oxygen of the NarG-Gly⁵⁰ amide is ∼3.4 Å from the N-7 of the purine bicycle. The amine nitrogen of NarG-Asn⁵² is 3.0 Å from a Q-pterin dithiolene sulfur and 3.2 Å from a P-pterin dithiolene sulfur. The carbonyl oxygen of NarG-Cys⁵³ is 3.6 Å from the N-10 secondary amine of the P-pterin.