Sofia Pauleta

Citation:

Pauleta, S. R., Y. Lu, C. F. Goodhew, I. Moura, G. W. Pettigrew, and J. A. Shelnutt. "Calcium-dependent heme structure in the reduced forms of the bacterial cytochrome c peroxidase from Paracoccus pantotrophus." Biochemistry. 47 (2008): 5841-5850.

Abstract:

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 Ca2+, 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 Ca2+, 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 Ca2+ 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 Ca2+-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 Ca2+, the resonance Raman spectra show that the peroxidatic heme remains high-spin.

Notes:

Times Cited: 3 Pauleta, Sofia R. Lu, Yi Goodhew, Celia F. Moura, Isabel Pettigrew, Graham W. Shelnutt, John A.

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