Ultrafast dynamics and anionic active states of the flavin cofactor in cryptochrome and photolyase
Ultrafast dynamics and anionic active states of the flavin cofactor in cryptochrome and photolyase
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DOI：
10.1021/ja801152h
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发表时间：
2008-06-18
影响因子：
15
通讯作者：
Zhong, Dongping
中科院分区：
文献类型：
--
作者：
Kao, Ya-Ting;Tan, Chuang;Zhong, Dongping
在这里，我们报告我们的系统研究的四个氧化还原态的黄素辅因子的光解酶和昆虫1型隐花色素的动力学。利用飞秒分辨率，我们观察到氧化态黄素腺嘌呤二核苷酸（FAD）在亚皮秒和中性自由基半醌（FADH（中心点））在几十皮秒通过蛋白质内电子转移主要与相邻的保守色氨酸三联体的超快光还原。这种超快的动力学使得这些形式的黄素不太可能是光裂合酶/隐花色素家族的功能状态。与此相反，我们发现，激发时的阴离子半醌（FAD（中心点-））和氢醌（FADH（-））具有更长的寿命，是兼容的高效分子间电子转移反应。在光解酶中，激发活性态（FADH（-*））具有长（纳秒）寿命，最适合DNA修复功能。在已知为蓝光光感受器的昆虫1型隐花色素中，激发的活性形式（FAD（中心点-*））在从几皮秒到几百皮秒的时间尺度上具有复杂的失活动力学，这被认为是通过具有柔性弯曲运动的锥形交叉点发生的，以调节功能通道。阴离子黄素的这些独特性质表明了光解酶/隐花色素蓝光光受体家族的初始功能步骤的电子转移的普遍机制。
We report here our systematic studies of the dynamics of four redox states of the flavin cofactor in both photolyases and insect type 1 cryptochromes. With femtosecond resolution, we observed ultrafast photoreduction of oxidized state flavin adenine dinucleotide (FAD) in subpicosecond and of neutral radical semiquinone (FADH(center dot)) in tens of picoseconds through intraprotein electron transfer mainly with a neighboring conserved tryptophan triad. Such ultrafast dynamics make these forms of flavin unlikely to be the functional states of the photolyase/cryptochrome family. In contrast, we find that upon excitation the anionic semiquinone (FAD(center dot-)) and hydroquinone (FADH(-)) have longer lifetimes that are compatible with high-efficiency intermolecular electron transfer reactions. In photolyases, the excited active state (FADH(-*)) has a long (nanosecond) lifetime optimal for DNA-repair function. In insect type 1 cryptochromes known to be blue-light photoreceptors; the excited active form (FAD(center dot-*)) has complex deactivation dynamics on the time scale from a few to hundreds of picoseconds, which is believed to occur through conical intersection(s) with a flexible bending motion to modulate the functional channel. These unique properties of anionic flavins suggest a universal mechanism of electron transfer for the initial functional steps of the photolyase/cryptochrome blue-light photoreceptor family.