title: Photoactivation of the flavin cofactor in Xenopus laevis (6 - 4) photolyase: observation of a transient tyrosyl radical by time-resolved electron paramagnetic resonance.
abstract: The light-induced electron transfer reaction of flavin cofactor photoactivation in Xenopus laevis (6-4) photolyase has been studied by continuous-wave and time-resolved electron paramagnetic resonance spectroscopy. When the photoactivation is initiated from the fully oxidized form of the flavin, a neutral flavin radical is observed as a long-lived paramagnetic intermediate of two consecutive single-electron reductions under participation of redox-active amino acid residues. By time-resolved electron paramagnetic resonance, a spin-polarized transient radical-pair signal was detected that shows remarkable differences to the signals observed in the related cyclobutane pyrimidine dimer photolyase enzyme. In (6-4) photolyase, a neutral tyrosine radical has been identified as the final electron donor, on the basis of the characteristic line width, hyperfine splitting pattern, and resonance magnetic field position of the tyrosine resonances of the transient radical pair.
authors.affiliation: Free University Berlin, Institute of Experimental Physics, Arnimallee 14, 14195 Berlin, Germany. stefan.weber@physik.fu-berlin.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
authors.forename: Christopher W M
authors.initials: CW
authors.lastname: Kay
authors.forename: Heike
authors.initials: H
authors.lastname: Mögling
authors.forename: Klaus
authors.initials: K
authors.lastname: Möbius
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hitomi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Todo
mesh_terms: D000818:Animals; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005292:Ferricyanides / Q000493:pharmacokinetics; D007700:Kinetics; D010084:Oxidation-Reduction; D010777:Photochemistry; D011487:Protein Conformation; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D005292:Ferricyanides; C098727:pyrimidine(6-4)pyrimidone photolyase; D004255:Deoxyribodipyrimidine Photo-Lyase; C028033:potassium ferricyanide