title: The unusual redox properties of flavocytochrome P450 BM3 flavodoxin domain.
abstract: Flavocytochrome P450 BM3 FMN domain is unique among the family of flavodoxins and homologues, in not forming a stable neutral blue FMN semiquinone radical. Anaerobic, one-electron reduction of the isolated domain over the pH 7-9.5 range showed that it forms an anionic red semiquinone that disproportionates slowly (0.014s(-1) at pH 7). The rate of disproportionation decreased at higher pH, indicating that protonation of the anionic semiquinone is an important feature of the mechanism. The reduction potential for the oxidised-semiquinone couple was determined to be -240mV and was largely independent of pH. The semiquinone appears, therefore, to be kinetically trapped by a slow protonation event, enabling it to act as a low-potential electron donor to the P450 heme.
authors.affiliation: School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK.
authors.forename: Sinead C
authors.initials: SC
authors.lastname: Hanley
authors.forename: Tobias W B
authors.initials: TW
authors.lastname: Ost
authors.forename: Simon
authors.initials: S
authors.lastname: Daff
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry*; D044927:Electron-Transferring Flavoproteins; D004789:Enzyme Activation; D005418:Flavodoxin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000737:chemistry*; D009251:NADPH-Ferrihemoprotein Reductase; D010084:Oxidation-Reduction; D017434:Protein Structure, Tertiary
chemical_list: D001426:Bacterial Proteins; D044927:Electron-Transferring Flavoproteins; D005418:Flavodoxin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D009251:NADPH-Ferrihemoprotein Reductase; C052423:flavocytochrome P450 BM3 monoxygenases