Structural intermediate in the photocycle of a BLUF (sensor of blue light using FAD) protein Slr1694 in a cyanobacterium Synechocystis sp PCC6803
Structural intermediate in the photocycle of a BLUF (sensor of blue light using FAD) protein Slr1694 in a cyanobacterium Synechocystis sp PCC6803
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DOI：
10.1021/bi048671n
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发表时间：
2004-11-30
期刊：
影响因子：
2.9
通讯作者：
Ono, T
中科院分区：
文献类型：
--
作者：
Hasegawa, K;Masuda, S;Ono, T
集胞藻PCC 6803中的Slr 1694是一个基于黄素腺嘌呤二核苷酸（FAD）的蓝光光感受器家族，称为BLUF（使用FAD的蓝光传感器）蛋白，其包括来自球形红细菌的AppA和来自纤细裸藻的PAC。在15 degreesC的暗态Slr 1694的照明可逆地诱导了信号光状态，其特征在于在UV-可见光谱中的红移和由光诱导的傅里叶变换红外（FTIR）差光谱的结合黄素和载脂蛋白的结构变化。中低温（-35 ℃）下的光照导致紫外-可见光谱的红移，尽管光诱导的变化有一些小的差异。相比之下，-35 ℃的光照导致完全不同的光诱导FTIR光谱，其中除了FAD异咯嗪环的C4=O键合变化的谱带之外，几乎所有谱带都被抑制。C4=O带在-35 ℃下以几乎相同的强度被诱导，但是光态的带频率被上移了6 cm（-1）。光态C4=0带的频率变化和其他带的振幅变化显示出相同的温度依赖性，半变化温度约为-20 ℃。结果表明，低温下，光诱导的载脂蛋白和FAD结构变化受到抑制，但与C4=O基团的氢键变化除外。光诱导的FTIR谱带的形成同样受到样品脱水的抑制。我们讨论了这种受约束的光态是光循环中的一个被捕获的中间态的可能性。
Slr1694 in Synechocystis sp. PCC6803 is a family of blue-light photoreceptors based on flavin adenine dinucleotide (FAD) called BLUF (sensor of blue light using FAD) proteins, which include AppA from Rhodobacter sphaeroides and PAC from Euglena gracilis. Illumination of dark-state Slr1694 at 15 degreesC reversibly induced a signaling light state characterized by the red shift in the UV-visible spectrum and by the light-induced Fourier transform infrared (FTIR) difference spectrum for structural changes of a bound flavin and apo protein. Illumination at the medium-low temperature (-35 degreesC) led to the red shift in the UV-visible spectrum despite some small difference in the light-induced changes. In contrast, the -35 degreesC illumination resulted in a completely different light-induced FTIR spectrum, in which almost all of the bands were suppressed with the exception of the bands for the change of C4=O bonding of the FAD isoalloxazine ring. The C4=O bands were induced at -35 degreesC with almost the same intensity, but the band frequency for the light state was upshifted by 6 cm(-1). The changes in frequency of the light-state C4=0 band and in amplitude of other bands showed the same temperature dependence with a half-change temperature at approximately -20 degreesC. It was indicated that the light-induced structural changes of apo protein and FAD were inhibited at low temperature with the exception of the change in hydrogen bonding to the C4=O group. The light-induced formation of the FTIR bands was similarly inhibited by sample dehydration. We discussed the possibility that this constrained light state is a trapped intermediate state in the photocycle of Slr1694.