The signaling state of Arabidopsis cryptochrome 2 contains flavin semiquinone
The signaling state of Arabidopsis cryptochrome 2 contains flavin semiquinone
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DOI：
10.1074/jbc.m700616200
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发表时间：
2007-05-18
影响因子：
4.8
通讯作者：
Batschauer, Alfred
中科院分区：
文献类型：
--
作者：
Banerjee, Roopa;Schleicher, Erik;Batschauer, Alfred
隐花色素 (Cry) 光感受器与 DNA 修复酶 DNA 光裂解酶具有高度的序列和结构相似性，并携带相同的黄素辅因子。因此，DNA光裂解酶被认为是隐花色素光激活过程的模型系统。与这一观点一致的是，最近对 CryDASH 亚家族隐花色素的光谱研究表明，黄素腺嘌呤二核苷酸 (FAD) 辅因子光还原至完全还原形式。然而，CryDASH 成员最近被证明对单链 DNA 中的环丁烷嘧啶二聚体具有光裂合酶活性，而隐花色素/光裂合酶家族的其他成员则不具备这种活性。因此，CryDASH 可能具有与密码色素不同的功能。隐花色素家族其他成员的光周期仍然难以捉摸，例如拟南芥 Cry1 和 Cry2，它们缺乏 DNA 修复活性，但控制光形态发生和开花时间。在这里，我们表明拟南芥 Cry2 经历光循环，其中半还原黄素 (FADH(.)) 在蓝光照射下积累。 Cry2 的绿光照射会导致黄素氧化态平衡发生变化，并减弱 Cry2 控制的反应，例如开花。这些结果表明，Cry2 的活性形式含有 FADH(.)（而催化活性光裂合酶需要完全还原的黄素 (FADH(.)）），并表明隐花色素可以代表光感受器，使用黄素氧化还原态进行信号传导，与用于光修复的 DNA 光裂合酶不同。
Cryptochrome ( Cry) photoreceptors share high sequence and structural similarity with DNA repair enzyme DNA-photolyase and carry the same flavin cofactor. Accordingly, DNA-photolyase was considered a model system for the light activation process of cryptochromes. In line with this view were recent spectroscopic studies on cryptochromes of the CryDASH subfamily that showed photoreduction of the flavin adenine dinucleotide ( FAD) cofactor to its fully reduced form. However, CryDASH members were recently shown to have photolyase activity for cyclobutane pyrimidine dimers in single-stranded DNA, which is absent for other members of the cryptochrome/photolyase family. Thus, CryDASH may have functions different from cryptochromes. The photocycle of other members of the cryptochrome family, such as Arabidopsis Cry1 and Cry2, which lack DNA repair activity but control photomorphogenesis and flowering time, remained elusive. Here we have shown that Arabidopsis Cry2 undergoes a photocycle in which semireduced flavin ( FADH(.)) accumulates upon blue light irradiation. Green light irradiation of Cry2 causes a change in the equilibrium of flavin oxidation states and attenuates Cry2-controlled responses such as flowering. These results demonstrate that the active form of Cry2 contains FADH(.) ( whereas catalytically active photolyase requires fully reduced flavin ( FADH(.))) and suggest that cryptochromes could represent photoreceptors using flavin redox states for signaling differently from DNA-photolyase for photorepair.