Assignment of Hyperfine-Shifted Resonances in Low-Spin Forms of Cytochrome c Peroxidase by Reconstitutions with Deuterated Hemins

Proton magnetic resonance assignments of protons from peripheral heme substituents have been carried out for two low-spin forms of cytochrome c peroxidase: CcP-CN and CcP-N3. The assignments were made by reconstituting CcP with six specifically deuterated protohemin IX derivatives. The results indícate that the pattern of unpaired π spin-density delocalization is consistent with an interpretation whereby the source of the rhombic perturbation is the orientation of the proximal histidine\u27s imidazole plane. However, we also present evidence that a specific interaction between pyrrole II and tryptophan 51 affects the observed shift pattern, thereby contributing to the rhombic perturbation. © 1983, American Chemical Society. All rights reserved