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首页> 外文期刊>Biochemistry >Blue-light-induced changes in Arabidopsis cryptochrome 1 probed by FTIR difference spectroscopy
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Blue-light-induced changes in Arabidopsis cryptochrome 1 probed by FTIR difference spectroscopy

机译：FTIR差光谱法探测蓝光诱导的拟南芥隐色染料1的变化

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Cryptochromes are blue-light photoreceptors that regulate a variety of responses in animals and plants, including circadian entrainment in Drosophila and photomorphogenesis in Arabidopsis. They comprise a photolyase homology region (PHR) of about 500 amino acids and a C-terminal extension of varying length. In the PHR domain, flavin adenine dinucleotide (FAD) is noncovalently bound. The presence of a second chromophore, such as methenyltetrahydrofolate, in animal and plant cryptochromes is still under debate. Arabidopsis cryptochrome 1 (CRY1) has been intensively studied with regard to function and interaction of the protein in vivo and in vitro. However, little is known about the pathway from light absorption to signal transduction on the molecular level. We investigated the full-length CRY1 protein by Fourier transform infrared (FTIR) and UV/vis difference spectroscopy. Starting from the fully oxidized state of the chromophore FAD, a neutral flavoprotein radical is formed upon illumination in the absence of any exogenous electron donor. A preliminary assignment of the chromophore bands is presented. The FTIR difference spectrum reveals only moderate changes in secondary structure of the apoprotein in response to the photoreduction of the chromophore. Deprotonation of an aspartic or glutamic acid, probably D396, accompanies radical formation, as is deduced from the negative band at 1734 cm(-1) in D2O. The main positive band at 1524 cm(-1) in the FTIR spectrum shows a strong shift to lower frequencies as compared to other flavoproteins. Together with the unusual blue-shift of the absorption in the visible range to 595 nm, this clearly distinguishes the radical form of CRY1 from those of structurally highly homologous DNA photolyases. As a consequence, the direct comparison of cryptochrome to photolyase in terms of photoreactivity and mechanism has to be made with caution.
机译：隐色是调节动物和植物中各种反应的蓝光感光体，包括果蝇中的昼夜节律夹带和拟南芥中的光形态发生。它们包含约500个氨基酸的光裂解酶同源区域（PHR）和可变长度的C末端延伸。在PHR域中，黄素腺嘌呤二核苷酸（FAD）是非共价结合的。动植物隐色色素中是否存在第二种生色团（例如亚甲基四氢叶酸）仍在争论中。关于该蛋白在体内和体外的功能和相互作用，已经对拟南芥（Arabidopsis cryptochrome）1（CRY1）进行了深入研究。然而，在分子水平上从光吸收到信号转导的途径知之甚少。我们通过傅里叶变换红外（FTIR）和紫外/可见差光谱法研究了全长CRY1蛋白。从生色团FAD的完全氧化状态开始，在不存在任何外源电子供体的情况下照射后会形成中性黄素蛋白自由基。提出了生色团带的初步分配。 FTIR差异光谱显示响应生色团的光还原，载脂蛋白的二级结构仅发生中等变化。天冬氨酸或谷氨酸的去质子化，可能是D396，伴随着自由基的形成，这是从D2O中1734 cm（-1）处的负带推导出来的。与其他黄素蛋白相比，FTIR光谱中1524 cm（-1）处的主要正带显示出向较低频率的强烈迁移。再加上在可见光范围至595 nm处吸收的异常蓝移，这清楚地将CRY1的自由基形式与结构高度同源的DNA光解酶的自由基形式区分开来。结果，必须谨慎地将隐色染料与光裂解酶在光反应性和机理方面进行直接比较。

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