title: Relationships of ligand binding, redox properties, and protonation in Coprinus cinereus peroxidase.
abstract: The pH dependence of the redox potentials and kinetics for CO association and dissociation was determined between pH 3.0 and 13.0 at 25 degrees C for the wild-type Coprinus cinereus fungal peroxidase and for a site-directed mutant in which Asp245, which is H-bonded to N delta of the imidazole of the proximal His183, was substituted with Asn. The determination of these functional properties allowed this information to be merged in a self-consistent fashion and to formulate for the first time a complete scheme employing the minimum number of groups required to describe the whole proton-linked behavior of both redox and ligand binding properties. The overall pH dependence can be accounted for by four redox- and ligand-linked groups. The proximal H-bond, which is strictly conserved in all peroxidases, will still be present in the site-specific mutant, but will no longer have an ionic character, and this event will bring about an alteration of redox equilibria and CO binding kinetics, envisaging a relevant role played by this H-bond also in modulating redox properties and ligand binding equilibria.
authors.affiliation: Department of Experimental Medicine and Biochemical Sciences, Università di Roma Tor Vergata, Via Montpellier 1, I-00133 Roma, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Ciaccio
authors.forename: Antonella
authors.initials: A
authors.lastname: Rosati
authors.forename: Giampiero
authors.initials: G
authors.lastname: De Sanctis
authors.forename: Federica
authors.initials: F
authors.lastname: Sinibaldi
authors.forename: Stefano
authors.initials: S
authors.lastname: Marini
authors.forename: Roberto
authors.initials: R
authors.lastname: Santucci
authors.forename: Paolo
authors.initials: P
authors.lastname: Ascenzi
authors.forename: Karen G
authors.initials: KG
authors.lastname: Welinder
authors.forename: Massimo
authors.initials: M
authors.lastname: Coletta
mesh_terms: D001665:Binding Sites; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003302:Coprinus / Q000201:enzymology*; D006418:Heme / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011522:Protons; D013053:Spectrophotometry; D013329:Structure-Activity Relationship
chemical_list: D008024:Ligands; D011522:Protons; D006418:Heme; D009195:Peroxidase