G4DFsc is a de novo designed single-chain four-helix bundle protein created to mimic the properties of di-iron carboxylate enzymes. The active site of G4DFsc is comprised of two iron atoms ligated by two histidine and four carboxylate residues. Flavin-dependent nitric oxide reductase (FprA) is a di-iron protein which contains 4-His/3-carboyxlate iron-binding motif and initiates the reduction of NO to N2O and H2O. To understand how FprA optimizes the enzyme for NO reduction relative to O2 dependent oxidation, two G4DFsc variants with 4-His/3-carboxylate active sites have been created (E11H-3HisG4DFsc and E44H-G4DFsc). The mutated proteins retain their helical structure but differ in their metal stoichiometry. Both proteins are capable of oxygenase activity, but E11H-3HisG4DFsc does not catalyze NO reduction. Structural and spectroscopic studies are being used to understand these differences in reactivity.

Structural and functional characterization of G4DFsc variants containing a 4-His/3-carboxylate active site

251st National Meeting (2016)

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