title: Photoreduction of the folate cofactor in members of the photolyase family.
abstract: Cryptochromes and DNA photolyases are related flavoproteins with flavin adenine dinucleotide as the common cofactor. Whereas photolyases repair DNA lesions caused by UV radiation, cryptochromes generally lack repair activity but act as UV-A/blue light photoreceptors. Two distinct electron transfer (ET) pathways have been identified in DNA photolyases. One pathway uses within its catalytic cycle, light-driven electron transfer from FADH(-)* to the DNA lesion and electron back-transfer to semireduced FADH(o) after photoproduct cleavage. This cyclic ET pathway seems to be unique for the photolyase subfamily. The second ET pathway mediates photoreduction of semireduced or fully oxidized FAD via a triad of aromatic residues that is conserved in photolyases and cryptochromes. The 5,10-methenyltetrahydrofolate (5,10-methenylTHF) antenna cofactor in members of the photolyase family is bleached upon light excitation. This process has been described as photodecomposition of 5,10-methenylTHF. We show that photobleaching of 5,10-methenylTHF in Arabidopsis cry3, a member of the cryptochrome DASH family, with repair activity for cyclobutane pyrimidine dimer lesions in single-stranded DNA and in Escherichia coli photolyase results from reduction of 5,10-methenylTHF to 5,10-methyleneTHF that requires the intact tryptophan triad. Thus, a third ET pathway exists in members of the photolyase family that remained undiscovered so far.
authors.affiliation: Faculty of Biology, Department of Plant Physiology and Photobiology, Philipps University, Marburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Moldt
authors.forename: Richard
authors.initials: R
authors.lastname: Pokorny
authors.forename: Christian
authors.initials: C
authors.lastname: Orth
authors.forename: Uwe
authors.initials: U
authors.lastname: Linne
authors.forename: Yann
authors.initials: Y
authors.lastname: Geisselbrecht
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Marahiel
authors.forename: Lars-Oliver
authors.initials: LO
authors.lastname: Essen
authors.forename: Alfred
authors.initials: A
authors.lastname: Batschauer
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins; D056931:Cryptochromes; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000378:metabolism*; D004583:Electrons; D004926:Escherichia coli / Q000378:metabolism*; D005420:Flavoproteins / Q000378:metabolism; D008027:Light; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D016297:Mutagenesis, Site-Directed; D011740:Pyrimidine Dimers / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013053:Spectrophotometry / Q000379:methods; D013763:Tetrahydrofolates / Q000737:chemistry
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D005420:Flavoproteins; D011740:Pyrimidine Dimers; D013763:Tetrahydrofolates; C018092:5,10-methenyltetrahydrofolate; D004255:Deoxyribodipyrimidine Photo-Lyase