The pH-induced selectivity between cysteine or histidine coordinated heme in an artificial α-helical metalloprotein
Koebke, Karl J.
Pecoraro, Vincent L.
De Novo metalloprotein design assesses the relationship between metal active site architecture and catalytic reactivity. Herein, we use an α-helical scaffold to control the iron coordination geometry when a heme cofactor is allowed to bind to either histidine or cysteine ligands, within a single artificial protein. Consequently, we uncovered a reversible pH-induced switch of the heme axial ligation within this simplified scaffold. Characterization of the specific heme coordination modes was done by using UV-Vis and Electron Paramagnetic Resonance spectroscopies. The penta- or hexa-coordinate thiolate heme (9 ≤ pH ≤ 11) and the penta-coordinate imidazole heme (6 ≤ pH ≤ 8.5) reproduces well the heme ligation in chloroperoxidases or cyt P450 monooxygenases and peroxidases, respectively. The stability of heme coordination upon ferric/ferrous redox cycling is a crucial property of the construct. At basic pHs, the thiolate mini-heme protein can catalyze O2 reduction when adsorbed onto a pyrolytic graphite electrode.
Accepted author manuscript
De Novo protein design , Cyt P450 monooxygenase , Heme enzymes , Thiolate ligands , EPR spectroscopy
Koebke, K. J., Kühl, T., Lojou, E., Demeler, B., Schoepp-Cothenet, B., Iranzo, O., Pecoraro, V. L., & Ivancich, A. (2021). The pH-induced selectivity between cysteine or histidine coordinated heme in an artificial α-helical metalloprotein. Angewandte Chemie International Edition, 2021, 60(8), 3974-3978. https://doi.org/10.1002/anie.202012673