The 2‐His‐1‐Carboxylate Facial Triad — An Emerging Structural Motif in Mononuclear Non‐Heme Iron(II) Enzymes

Abstract

A 2‐His‐1‐carboxylate facial triad is a common feature of the active sites in a number of mononuclear non‐heme iron(II) enzymes. This structural motif was established crystallographically for five different classes of enzymes and inferred from sequence similarity for two other classes. The 2‐His‐1‐carboxylate facial triad anchors the iron in the active site and at the same time maintains three additional cis‐oriented sites. These sites can be used to bind other endogenous ligands or exogenous ligands such as substrate and/or O₂, giving the metal center great flexibility to use different mechanistic strategies to perform a variety of chemical transformations.