Zikihara Kazunori, Ishikawa Tomoko, Todo Takeshi, Tokutomi Satoru
Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan.
Photochem Photobiol. 2008 Jul-Aug;84(4):1016-23. doi: 10.1111/j.1751-1097.2007.00364.x. Epub 2008 May 20.
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 (FAD(ox)) in the dark. Blue light converts FAD(ox) to the neutral radical form (FADH*). Formed FADH* is transformed to the fully reduced form FADH(2) (or FADH(-)) by successive light irradiation, or reverts to FAD(ox). FADH(2) (or FADH(-)) reverts to FADH* or possibly to FAD(ox) 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.
利用紫外可见吸收光谱法，在293K的水溶液中研究了斑马鱼蓝光光感受器隐花色素-DASH（Cry-DASH）（隐花色素家族的新成员）的光反应。斑马鱼Cry-DASH非共价结合两个发色团，即黄素腺嘌呤二核苷酸（FAD）和N5,N10-亚甲基-5,6,7,8-四氢叶酸（MTHF）。结合的FAD在黑暗中以氧化形式（FAD(ox)）存在。蓝光将FAD(ox)转化为中性自由基形式（FADH*）。通过连续光照，形成的FADH转变为完全还原形式FADH(2)（或FADH(-)），或恢复为FAD(ox)。FADH(2)（或FADH(-)）直接恢复为FADH或可能恢复为FAD(ox)。二硫苏糖醇的作用表明斑马鱼Cry-DASH中的FAD与外部介质中的还原剂之间可能存在电子转移。这是关于脊椎动物Cry-DASH家族蛋白光反应途径和动力学的首次报道。
