title: Photoadduct Formation from the FMN Singlet Excited State in the LOV2 Domain of Chlamydomonas reinhardtii Phototropin.
abstract: The two light, oxygen, and voltage domains of phototropin are blue-light photoreceptor domains that control various functions in plants and green algae. The key step of the light-driven reaction is the formation of a photoadduct between its FMN chromophore and a conserved cysteine, where the canonical reaction proceeds through the FMN triplet state. Here, complete photoreaction mapping of CrLOV2 from Chlamydomonas reinhardtii phototropin and AsLOV2 from Avena sativa phototropin-1 was realized by ultrafast broadband spectroscopy from femtoseconds to microseconds. We demonstrate that in CrLOV2, a direct photoadduct formation channel originates from the initially excited singlet state, in addition to the canonical reaction through the triplet state. This direct photoadduct reaction is coupled by a proton or hydrogen transfer process, as indicated by a significant kinetic isotope effect of 1.4 on the fluorescence lifetime. Kinetic model analyses showed that 38% of the photoadducts are generated from the singlet excited state.
authors: Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit , 1081 De Boelelaan, 1081 HV Amsterdam, The Netherlands.
authors: Jingyi
authors: J
authors: Zhu
authors: Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit , 1081 De Boelelaan, 1081 HV Amsterdam, The Netherlands.
authors: Tilo
authors: T
authors: Mathes
authors: Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit , 1081 De Boelelaan, 1081 HV Amsterdam, The Netherlands.
authors: Yusaku
authors: Y
authors: Hontani
authors: Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit , 1081 De Boelelaan, 1081 HV Amsterdam, The Netherlands.
authors: Maxime T A
authors: MT
authors: Alexandre
authors: Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit , 1081 De Boelelaan, 1081 HV Amsterdam, The Netherlands.
authors: K C
authors: KC
authors: Toh
authors: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.
authors: Peter
authors: P
authors: Hegemann
authors: Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit , 1081 De Boelelaan, 1081 HV Amsterdam, The Netherlands.
authors: John T M
authors: JT
authors: Kennis
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000737:chemistry*; D005486:Flavin Mononucleotide / Q000737:chemistry*; D010777:Photochemistry / Q000379:methods*; D056949:Phototropins / Q000737:chemistry*
chemical_list: D056949:Phototropins; D005486:Flavin Mononucleotide