Altering the O(2)-Dependent Reactivity of de novo Due Ferri Proteins

De novo proteins provide a unique opportunity for investigating the structure-function relationships of metalloproteins in a minimal, well-defined, and controlled scaffold. Herein, we describe the rational programming of function in a de novo designed di-iron carboxylate protein from the due ferri family. Originally created to catalyze O(2)-dependent, two-electron oxidation of hydroquinones, the protein was reprogrammed to catalyze the selective N-hydroxylation of arylamines by remodeling the substrate access cavity and introducing a critical third His ligand to the metal binding cavity. Additional second-and third-shell modifications were required to stabilize the His ligand in the core of the protein. These changes resulted in at least a 10(6 –)fold increase in the relative rates of the two reactions. This result highlights the potential for using de novo proteins as scaffolds for future investigations of geometric and electronic factors that influence the catalytic tuning of di-iron active sites.