Proton NMR Studies of the Electronic and Molecular Structure of Ferric Low-Spin Horseradish Peroxidase Complexes
High-field proton NMR studies of native and reconstituted horseradish peroxidase (HRP) were used to investigate the electronic and physical structure of the heme pocket in three ferric low-spin forms of the protein. Reconstitution of selectively deuterium labeled hemes into apo-HRP led to the definitive assignment of many hyperfine shifted peaks. Consideration of line width, pH titration data, and the effect of heme peripheral substituents has permitted the assignment of additional heme as well as proximal histidine peaks. Variable temperature data present further evidence of tight heme-apoprotein contacts in HRP. It is shown that the transition of the cyanide complex of HRP at high pH to a new cyanide-ligated alkaline form is consistent with a change in axial magnetic anisotropy. At high pH resting state HRP undergoes a more drastic change in spectrum and structure that is attributed to coordination of a distal histidine in a configuration with its imidazole deprotonated and its π plane oriented essentially perpendicular to that of the proximal histidyl imidazole. © 1984, American Chemical Society. All rights reserved.
Publication Source (Journal or Book title)
Journal of the American Chemical Society
de Ropp, J., La Mar, G., Smith, K., & Langry, K. (1984). Proton NMR Studies of the Electronic and Molecular Structure of Ferric Low-Spin Horseradish Peroxidase Complexes. Journal of the American Chemical Society, 106 (16), 4438-4444. https://doi.org/10.1021/ja00328a025