title: Light-induced electron transfer in Arabidopsis cryptochrome-1 correlates with in vivo function.
abstract: Cryptochromes are blue light-activated photoreceptors found in multiple organisms with significant similarity to photolyases, a class of light-dependent DNA repair enzymes. Unlike photolyases, cryptochromes do not repair DNA and instead mediate blue light-dependent developmental, growth, and/or circadian responses by an as yet unknown mechanism of action. It has recently been shown that Arabidopsis cryptochrome-1 retains photolyase-like photoreduction of its flavin cofactor FAD by intraprotein electron transfer from tryptophan and tyrosine residues. Here we demonstrate that substitution of two conserved tryptophans that are constituents of the flavin-reducing electron transfer chain in Escherichia coli photolyase impairs light-induced electron transfer in the Arabidopsis cryptochrome-1 photoreceptor in vitro. Furthermore, we show that these substitutions result in marked reduction of light-activated autophosphorylation of cryptochrome-1 in vitro and of its photoreceptor function in vivo, consistent with biological relevance of the electron transfer reaction. These data support the possibility that light-induced flavin reduction via the tryptophan chain is the primary step in the signaling pathway of plant cryptochrome.
authors.affiliation: Université Paris VI, Casier 156, Paris, France.
authors.forename: Anke
authors.initials: A
authors.lastname: Zeugner
authors.forename: Martin
authors.initials: M
authors.lastname: Byrdin
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Bouly
authors.forename: Nadia
authors.initials: N
authors.lastname: Bakrim
authors.forename: Baldissera
authors.initials: B
authors.lastname: Giovani
authors.forename: Klaus
authors.initials: K
authors.lastname: Brettel
authors.forename: Margaret
authors.initials: M
authors.lastname: Ahmad
mesh_terms: D019943:Amino Acid Substitution; D000872:Anthocyanins / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D056931:Cryptochromes; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005420:Flavoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008027:Light; D016297:Mutagenesis, Site-Directed; D018462:Photobiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014364:Tryptophan / Q000737:chemistry
chemical_list: D000872:Anthocyanins; D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D005420:Flavoproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D005182:Flavin-Adenine Dinucleotide; D014364:Tryptophan; D004255:Deoxyribodipyrimidine Photo-Lyase