Rescue of the horseradish peroxidase His-170-Ala mutant activity by imidazole: importance of proximal ligand tethering

The mutant horseradish peroxidase (HRP) designated as H170A hHRP was prepared and analyzed by Raman spectroscopy. The H170A hHRP mutant is composed of an iron molecule that is strongly coordinated by two axial ligands that are distinct from the wild type hHRP. The alterations in the heme molecules of H170A hHRP affected the bond lengths of its axial ligands. Myoglobin also affected the bonds of the proximal and distal ligands of HRP.