title: Calcium-dependent conformation of a heme and fingerprint peptide of the diheme cytochrome c peroxidase from Paracoccus pantotrophus.
abstract: The structural changes in the heme macrocycle and substituents caused by binding of Ca(2+) to the diheme cytochrome c peroxidase from Paracoccus pantotrophus were clarified by resonance Raman spectroscopy of the inactive fully oxidized form of the enzyme. The changes in the macrocycle vibrational modes are consistent with a Ca(2+)-dependent increase in the out-of-plane distortion of the low-potential heme, the proposed peroxidatic heme. Most of the increase in out-of-plane distortion occurs when the high-affinity site I is occupied, but a small further increase in distortion occurs when site II is also occupied by Ca(2+) or Mg(2+). This increase in the heme distortion explains the red shift in the Soret absorption band that occurs upon Ca(2+) binding. Changes also occur in the low-frequency substituent modes of the heme, indicating that a structural change in the covalently attached fingerprint pentapeptide of the LP heme occurs upon Ca(2+) binding to site I. These structural changes may lead to loss of the sixth ligand at the peroxidatic heme in the semireduced form of the enzyme and activation.
authors.affiliation: Centro de Química Fina e Biotecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2825 Monte de Caparica, Portugal.
authors.forename: S R
authors.initials: SR
authors.lastname: Pauleta
authors.forename: Y
authors.initials: Y
authors.lastname: Lu
authors.forename: C F
authors.initials: CF
authors.lastname: Goodhew
authors.forename: I
authors.initials: I
authors.lastname: Moura
authors.forename: G W
authors.initials: GW
authors.lastname: Pettigrew
authors.forename: J A
authors.initials: JA
authors.lastname: Shelnutt
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D003578:Cytochrome-c Peroxidase / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010230:Paracoccus / Q000201:enzymology*; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics
chemical_list: D010446:Peptide Fragments; D006418:Heme; D003578:Cytochrome-c Peroxidase; D002118:Calcium