Thu, 21 Aug 2008 14:00:01 BST CiteULike: neils's Pauleta http://www.citeulike.org/user/neils/author/Pauleta CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/neils/article/2732440 <i>Biochemistry (29 April 2008)</i><br /><br />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 ³15 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. Calcium-Dependent Heme Structure in the Reduced Forms of the Bacterial Cytochrome c Peroxidase from Paracoccus pantotrophus Sofia Pauleta Yi Lu Celia Goodhew Isabel Moura Graham Pettigrew John Shelnutt doi:10.1021/bi702486d Biochemistry (29 April 2008) 2008-04-29T08:20:34-00:00 2008 Biochemistry calcium cytochrome haem paracoccus peroxidase structure