Involvement of Electron Transfer in the Photoreaction of Zebrafish Cryptochrome-DASH

Authors

  • Kazunori Zikihara,

    1. Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai,  Osaka, Japan
    2. Radiation Biology Center, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
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  • Tomoko Ishikawa,

    1. Radiation Biology Center, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
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    • §Current address: Department of Radiation Biology and Medical Genetics, Graduate School of Medicine, Osaka University, B4, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.

  • Takeshi Todo,

    1. Radiation Biology Center, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
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    • §Current address: Department of Radiation Biology and Medical Genetics, Graduate School of Medicine, Osaka University, B4, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.

  • Satoru Tokutomi

    Corresponding author
    1. Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai,  Osaka, Japan
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  • This invited paper is part of the Symposium-in-Print: Photoreceptors and Signal Transduction.

*Corresponding author email: toxan@b.s.osakafu-u.ac.jp (Satoru Tokutomi)

Abstract

Photoreaction of a blue-light photoreceptor Cryptochrome-DASH (Cry-DASH), a new member of the Cryptochrome family, from zebrafish was studied by UV–visible absorption spectroscopy in aqueous solutions at 293 K. Zebrafish Cry-DASH binds two chromophores, a flavin adenine dinucleotide (FAD) and a N5,N10-methenyl-5,6,7,8-tetrahydrofolate (MTHF) noncovalently. The bound FAD exists in the oxidized form (FADox) in the dark. Blue light converts FADox to the neutral radical form (FADH?). Formed FADH? is transformed to the fully reduced form FADH2 (or FADH) by successive light irradiation, or reverts to FADox. FADH2 (or FADH) reverts to FADH? or possibly to FADox directly. The effect of dithiothreitol suggests a possible electron transfer between FAD in zebrafish Cry-DASH and reductants in the external medium. This is the first report on the photoreaction pathway and kinetics of a vertebrate Cry-DASH family protein.

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