title: Light-generated paramagnetic intermediates in BLUF domains.
abstract: Blue-light sensitive photoreceptory BLUF domains are flavoproteins, which regulate various, mostly stress-related processes in bacteria and eukaryotes. The photoreactivity of the flavin adenine dinucleotide (FAD) cofactor in three BLUF domains from Rhodobacter sphaeroides, Synechocystis sp. PCC 6803 and Escherichia coli have been studied at low temperature using time-resolved electron paramagnetic resonance. Photoinduced flavin triplet states and radical-pair species have been detected on a microsecond time scale. Differences in the electronic structures of the FAD cofactors as reflected by altered zero-field splitting parameters of the triplet states could be correlated with changes in the amino-acid composition of the various BLUF domains' cofactor binding pockets. For the generation of the light-induced, spin-correlated radical-pair species in the BLUF domain from Synechocystis sp. PCC 6803, a tyrosine residue near the flavin's isoalloxazine moiety plays a critical role.
authors.affiliation: Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie, Freiburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
authors.forename: Claudia
authors.initials: C
authors.lastname: Schroeder
authors.forename: Sylwia
authors.initials: S
authors.lastname: Kacprzak
authors.forename: Tilo
authors.initials: T
authors.lastname: Mathes
authors.forename: Radoslaw M
authors.initials: RM
authors.lastname: Kowalczyk
authors.forename: Lars-Oliver
authors.initials: LO
authors.lastname: Essen
authors.forename: Peter
authors.initials: P
authors.lastname: Hegemann
authors.forename: Erik
authors.initials: E
authors.lastname: Schleicher
authors.forename: Robert
authors.initials: R
authors.lastname: Bittl
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D004926:Escherichia coli / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry / Q000378:metabolism*; D005415:Flavins / Q000378:metabolism*; D005420:Flavoproteins / Q000737:chemistry / Q000378:metabolism*; D005609:Free Radicals; D008027:Light; D055668:Photochemical Processes / Q000528:radiation effects; D020283:Photoreceptors, Microbial / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding / Q000528:radiation effects; D017434:Protein Structure, Tertiary / Q000528:radiation effects; D012242:Rhodobacter sphaeroides / Q000378:metabolism; D046939:Synechocystis / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005415:Flavins; D005420:Flavoproteins; D005609:Free Radicals; D020283:Photoreceptors, Microbial; D005182:Flavin-Adenine Dinucleotide; D014443:Tyrosine; C008173:isoalloxazine