Evidence of a light-sensing role for folate in Arabidopsis cryptochrome blue-light receptors
Evidence of a light-sensing role for folate in Arabidopsis cryptochrome blue-light receptors
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DOI：
10.1093/mp/ssm008
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发表时间：
2008-01-01
期刊：
影响因子：
27.5
通讯作者：
Ahmad, Margaret
中科院分区：
文献类型：
--
作者：
Hoang, Nathalie;Bouly, Jean-Pierre;Ahmad, Margaret
拟南芥隐花色素cry1和cry2是蓝光信号分子，与光解酶（一类蓝光敏感DNA修复酶）具有显著的结构相似性。与光裂合酶一样，纯化的植物隐花色素已被证明可以结合黄素和蝶呤发色团。黄素起着光传感器的作用，并对启动信号级联的蓝光做出反应。然而，蝶呤在植物隐花色素中的作用至今仍不清楚。在这里，我们表明，光依赖性降解cry2的作用光谱在380 nm处有一个显着的活性峰，与蝶呤辅因子的吸收一致。我们进一步表明，在活的昆虫细胞中表达的cry1蛋白响应更大的敏感性，380 nm的光比450 nm，与光捕获天线色素，将激发能量转移到氧化黄素cry1一致。蝶呤生物合成抑制剂DHAP选择性地降低隐花色素在380 nm，但不是450 nm的蓝光在这些细胞培养物的响应，表明天线色素是一个叶酸辅因子类似的光解酶。
Arabidopsis cryptochromes cry1 and cry2 are blue-light signalling molecules with significant structural similarity to photolyases - a class of blue-light-sensing DNA repair enzymes. Like photolyases, purified plant cryptochromes have been shown to bind both flavin and pterin chromophores. The flavin functions as a light sensor and undergoes reduction in response to blue light that initiates the signalling cascade. However, the role of the pterin in plant cryptochromes has until now been unknown. Here, we show that the action spectrum for light-dependent degradation of cry2 has a significant peak of activity at 380 nm, consistent with absorption by a pterin cofactor. We further show that cry1 protein expressed in living insect cells responds with greater sensitivity to 380 nm light than to 450 nm, consistent with a light-harvesting antenna pigment that transfers excitation energy to the oxidized flavin of cry1. The pterin biosynthesis inhibitor DHAP selectively reduces cryptochrome responsivity at 380 nm but not 450 nm blue light in these cell cultures, indicating that the antenna pigment is a folate cofactor similar to that of photolyases.