title: ATP binding turns plant cryptochrome into an efficient natural photoswitch.
abstract: Cryptochromes are flavoproteins that drive diverse developmental light-responses in plants and participate in the circadian clock in animals. Plant cryptochromes have found application as photoswitches in optogenetics. We have studied effects of pH and ATP on the functionally relevant photoreduction of the oxidized FAD cofactor to the semi-reduced FADH(·) radical in isolated Arabidopsis cryptochrome 1 by transient absorption spectroscopy on nanosecond to millisecond timescales. In the absence of ATP, the yield of light-induced radicals strongly decreased with increasing pH from 6.5 to 8.5. With ATP present, these yields were significantly higher and virtually pH-independent up to pH 9. Analysis of our data in light of the crystallographic structure suggests that ATP-binding shifts the pKa of aspartic acid D396, the putative proton donor to FAD·(-), from ~7.4 to >9, and favours a reaction pathway yielding long-lived aspartate D396(-). Its negative charge could trigger conformational changes necessary for signal transduction.
authors.affiliation: 1] UMR-8221, CEA-Institut de Biologie et de Technologie de Saclay, CNRS, Université Paris Sud, 91191 Gif-sur-Yvette, France [2] UR 5, Physiologie Cellulaire et Moléculaire des Plantes, Université Pierre et Marie Curie, CNRS, 75005 Paris 6, France.
authors.forename: Pavel
authors.initials: P
authors.lastname: Müller
authors.affiliation: 1] UR 5, Physiologie Cellulaire et Moléculaire des Plantes, Université Pierre et Marie Curie, CNRS, 75005 Paris 6, France [2] Department of Physics and Astronomy, University of California, Irvine, California 92697, USA [3].
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Bouly
authors.affiliation: 1] Department of Integrative Structural and Computational Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA [2].
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hitomi
authors.affiliation: UMR CNRS 7591, Laboratoire d'Electrochimie Moléculaire, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris 13, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Balland
authors.affiliation: Department of Integrative Structural and Computational Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Elizabeth D
authors.initials: ED
authors.lastname: Getzoff
authors.affiliation: Department of Physics and Astronomy, University of California, Irvine, California 92697, USA.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Ritz
authors.affiliation: UMR-8221, CEA-Institut de Biologie et de Technologie de Saclay, CNRS, Université Paris Sud, 91191 Gif-sur-Yvette, France.
authors.forename: Klaus
authors.initials: K
authors.lastname: Brettel
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000465:Algorithms; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism*; D056931:Cryptochromes / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011789:Quantum Theory; D015398:Signal Transduction / Q000528:radiation effects; D013056:Spectrophotometry, Ultraviolet
chemical_list: D029681:Arabidopsis Proteins; D056931:Cryptochromes; D000255:Adenosine Triphosphate