FTIR study on the hydrogen bond structure of a key tyrosine residue in the flavin-binding blue light sensor TePixD from Thermosynechococcus elongatus
FTIR study on the hydrogen bond structure of a key tyrosine residue in the flavin-binding blue light sensor TePixD from Thermosynechococcus elongatus
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DOI：
10.1021/bi7004653
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发表时间：
2007-06-05
期刊：
影响因子：
2.9
通讯作者：
Noguchi, Takumi
中科院分区：
文献类型：
--
作者：
Takahashi, Ryouta;Okajima, Koji;Noguchi, Takumi
BLUF（sensor of blue light using FAD）结构域是具有黄素分子作为活性辅因子的蓝光受体。一个保守的酪氨酸残基位于邻近黄素已被提出是一个关键的氨基酸的BLUF结构域的光反应机制。我们已经研究了这个关键的Tyr残基的结构和相关的蓝细菌Thermosynechococcus elongatus，TePixD的BLUF蛋白的光反应，通过傅里叶变换红外（FTIR）差光谱和密度泛函理论（DFT）计算。未标记和[4-C-13] Tyr标记的TePixD在H2O和D2 O中的光诱导FTIR差谱显示，光敏Tyr侧链的nu CO/delta COH振动在暗适应状态下位于1265/1242 cm（-1），在光诱导信号状态下位于1273/1235 cm（-1）。这些信号被分配到振动的Tyr 8附近的黄素从[4-C-13]Tyr标记的影响的情况下，在Tyr 8 Phe突变体。对甲苯酚与酰胺的氢键复合物作为Tyr 8-Gln 50相互作用的模型的DFT计算表明，Tyr 8作为Gln 50在暗态和亮态的氢键供体。进一步的DFT分析表明，这种氢键是加强后，光转换到轻态伴随着氢键角的变化。Tyr 8的氢键结构的变化可能通过Tyr 8-Gln 50-黄素氢键网络与黄素光反应耦合，表明Tyr 8在TePixD的光反应机制中起重要作用。
The BLUF (sensor of blue light using FAD) domain is a blue light receptor possessing a flavin molecule as an active cofactor. A conserved Tyr residue located adjacent to flavin has been proposed to be a key amino acid in the mechanism of the photoreaction of the BLUF domain. We have studied the structure of this key Tyr residue and the relevance to the photoreaction in the BLUF protein of the cyanobacterium Thermosynechococcus elongatus, TePixD, by means of Fourier transform infrared (FTIR) difference spectroscopy and density functional theory (DFT) calculations. Light-induced FTIR difference spectra of unlabeled and [4-C-13]Tyr-labeled TePixD in H2O and D2O revealed that the nu CO/delta COH vibrations of a photosensitive Tyr side chain are located at 1265/1242 cm(-1) in the dark-adapted state and at 1273/1235 cm(-1) in the light-induced signaling state. These signals were assigned to the vibrations of Tyr8 near flavin from the absence of the effect of [4-C-13]Tyr labeling in the Tyr8Phe mutant. DFT calculations of H-bonded complexes of p-cresol with amides as models of the Tyr8-Gln50 interactions showed that Tyr8 acts as a H-bond donor to the Gln50 in both of the dark and light states. Further DFT analysis suggested that this H-bond is strengthened upon photoconversion to the light state accompanied with a change in the H-bond angle. The change in the H-bond structure of Tyr8 is coupled to the flavin photoreaction probably through the Tyr8-Gln50-flavin H-bond network, suggesting a significant role of Tyr8 in the photoreaction mechanism of TePixD.