Calcium-Dependent Heme Structure in the Reduced Forms of the Bacterial Cytochrome c Peroxidase from Paracoccus pantotrophus
| Autor: | John A. Shelnutt, Sofia R. Pauleta, Isabel Moura, Graham W. Pettigrew, Celia F. Goodhew, Yi Lu |
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| Rok vydání: | 2008 |
| Předmět: |
Protein Conformation
Stereochemistry Molecular Conformation chemistry.chemical_element Heme Calcium Spectrum Analysis Raman Biochemistry Enzyme activator chemistry.chemical_compound Protein structure Cations medicine Magnesium Ions chemistry.chemical_classification Paracoccus pantotrophus Chemistry Cytochrome c peroxidase Cytochrome-c Peroxidase Enzyme Activation Oxygen Enzyme Models Chemical Ferric medicine.drug |
| Zdroj: | Biochemistry. 47:5841-5850 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | This work reports for the first time a resonance Raman study of the mixed-valence and fully reduced forms of Paracoccus pantotrophus bacterial cytochrome c peroxidase. The spectra of the active mixed-valence enzyme show changes in the structure of the ferric peroxidatic heme compared to the fully oxidized enzyme; these differences are observed upon reduction of the electron-transferring heme and upon full occupancy of the calcium site. For the mixed-valence form in the absence of Ca(2+), the peroxidatic heme is six-coordinate and low-spin on the basis of the frequencies of the structure-sensitive Raman lines: the enzyme is inactive. With added Ca(2+), the peroxidatic heme is five-coordinate high-spin and active. The calcium-dependent spectral differences indicate little change in the conformation of the ferrous electron-transferring heme, but substantial changes in the conformation of the ferric peroxidatic heme. Structural changes associated with Ca(2+) binding are indicated by spectral differences in the structure-sensitive marker lines, the out-of-plane low-frequency macrocyclic modes, and the vibrations associated with the heme substituents of that heme. The Ca(2+)-dependent appearance of a strong gamma 15 saddling-symmetry mode for the mixed-valence form is consistent with a strong saddling deformation in the active peroxidatic heme, a feature seen in the Raman spectra of other peroxidases. For the fully reduced form in the presence of Ca(2+), the resonance Raman spectra show that the peroxidatic heme remains high-spin. |
| Databáze: | OpenAIRE |
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