Active-Site Models of Bacterial Nitric Oxide Reductase Featuring Tris-Histidyl and Glutamic Acid Mimics:  Influence of a Carboxylate Ligand on Fe<sub>B</sub> Binding and the Heme Fe/Fe<sub>B</sub> Redox Potential

Active-site models of bacterial nitric oxide reductase (NOR) featuring a heme Fe and a trisimidazole- and glutaric acid-bound non-heme Fe (Fe<sub>B</sub>) have been synthesized. These models closely replicate the proposed active site of native NORs. Examination of these models shows that the glutamic acid mimic is required for both Fe<sub>B</sub> retention in the distal binding site and proper modulation of the redox potentials of both the heme and non-heme Fe's.