title: Crystal structure of cindoxin, the P450cin redox partner.
abstract: The crystal structure of the flavin mononucleotide (FMN)-containing redox partner to P450cin, cindoxin (Cdx), has been determined to 1.3 Å resolution. The overall structure is similar to that of the FMN domain of human cytochrome P450 reductase. A Brownian dynamics-molecular dynamics docking method was used to produce a model of Cdx with its redox partner, P450cin. This Cdx-P450cin model highlights the potential importance of Cdx Tyr96 in bridging the FMN and heme cofactors as well P450cin Arg102 and Arg346. Each of the single-site Ala mutants exhibits ~10% of the wild-type activity, thus demonstrating the importance of these residues for binding and/or electron transfer. In the well-studied P450cam system, redox partner binding stabilizes the open low-spin conformation of P450cam and greatly decreases the stability of the oxy complex. In sharp contrast, Cdx does not shift P450cin to a low-spin state, although the stability of oxy-P450cin is decreased 10-fold in the presence of Cdx. This indicates that Cdx may have a modest effect on the open-closed equilibrium in P450cin compared to that in P450cam. It has been postulated that part of the effector role of Pdx on P450cam is to promote a significant structural change that makes available a proton relay network involving Asp251 required for O2 activation. The structure around the corresponding Asp in P450cin, Asp241, provides a possible structural reason for why P450cin is less dependent on its redox partner for functionally important structural changes.
authors.affiliation: Departments of †Molecular Biology and Biochemistry, ‡Chemistry, and §Pharmaceutical Sciences, University of California , Irvine, California 92697-3900, United States.
authors.forename: Yarrow
authors.initials: Y
authors.lastname: Madrona
authors.forename: Scott A
authors.initials: SA
authors.lastname: Hollingsworth
authors.forename: Sarvind
authors.initials: S
authors.lastname: Tripathi
authors.forename: James B
authors.initials: JB
authors.lastname: Fields
authors.forename: Jean-Christophe N
authors.initials: JC
authors.lastname: Rwigema
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Tobias
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Poulos
mesh_terms: D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000378:metabolism*; D005486:Flavin Mononucleotide / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary
chemical_list: D005486:Flavin Mononucleotide; D003577:Cytochrome P-450 Enzyme System; C465212:cytochrome P-450 176A