Cryptochromes (CRYs) are evolutionarily conserved photoreceptors that mediate various light-induced responses in bacteria, plants, and animals. Plant cryptochromes govern a variety of critical growth and developmental processes including seed germination, flowering time and entrainment of the circadian clock. CRYs photocycle involves reduction of their flavin adenine dinucleotide (FAD)-bound chromophore, which is completely oxidized in the dark and semi-reduced in the light signalling-active state. Despite the significant progress in characterizing cryptochromes, important aspects of their photochemistry, regulation, and light-induced structural adaptation remain to be addressed. In this study, we determine the crystal structure of the photosensory domain of Arabidopsis CRY2 in a tetrameric active state. Systematic structure-based analyses of photo-activated and inactive plant CRYs elucidate new structural elements and critical residues that dynamically partake in photo-induced oligomerization. Our study offers an updated model of CRYs photoactivation mechanism as well as the mode of its regulation by interacting proteins.

中文翻译：

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植物Cryptochrome-2光活化的结构见解

隐色染料（CRYs）是进化保守的感光体，可介导细菌，植物和动物中各种光诱导的反应。植物隐花色素控制着各种关键的生长和发育过程，包括种子发芽，开花时间和生物钟的夹带。CRYs的光循环涉及还原其黄素腺嘌呤二核苷酸（FAD）结合的生色团，该生色团在黑暗中被完全氧化，在光信号激活状态下被半还原。尽管在表征隐色染料方面取得了重大进展，但其光化学，调节和光诱导的结构适应性的重要方面仍有待解决。在这项研究中，我们确定拟南芥CRY2的光敏结构域在四聚体活性状态下的晶体结构。基于系统结构的对光活化和无活性植物CRY的分析阐明了动态参与光诱导寡聚的新结构元素和关键残基。我们的研究提供了CRYs光激活机制的更新模型，以及通过相互作用蛋白调节其调控的模式。