Evidence for Tautomerisation of Glutamine in BLUF Blue Light Receptors by Vibrational Spectroscopy and Computational Chemistry.
Evidence for Tautomerisation of Glutamine in BLUF Blue Light Receptors by Vibrational Spectroscopy and Computational Chemistry.
复制标题
通过振动光谱和计算化学中的BLUF蓝光受体中谷氨酰胺互变异的证据。
DOI：
10.1038/srep22669
复制
发表时间：
2016-03-07
影响因子：
4.6
通讯作者：
Kottke T
中科院分区：
文献类型：
--
作者：
Domratcheva T;Hartmann E;Schlichting I;Kottke T
BLUF（使用黄素的蓝光传感器）结构域调节细菌和真核生物中各种酶效应结构域的活性。BLUF通过重组氢键网络具有独特的光活化特性，而不是氧化还原反应或发色团的异构化。靠近黄素发色团的一个保守的谷氨酰胺残基在光响应中起着核心作用，但潜在的修饰尚不清楚。我们用15N在两个具有代表性的blf区域标记谷氨酰胺，并进行了时间分辨红外双差光谱。信号的分配是通过广泛的量子化学计算在187个原子的大型模型上进行的，这些原子再现了blf光激活的紫外-可见和红外特征。在暗态，相对较低的频率为1667 cm−1分配给谷氨酰胺C=O接受酪氨酸的氢键。在光态下，在~ 1691 cm−1处用C=N拉伸提取了一个互变异构的谷氨酰胺的特征，通过15N标记显示出强烈的下移特征。此外，还发现了黄素C4=O拉伸的间接同位素效应。我们得出结论，蓝光受体的光激活不仅涉及氢键的重排，还包括蛋白质共价键的变化。
BLUF (blue light sensor using flavin) domains regulate the activity of various enzymatic effector domains in bacteria and euglenids. BLUF features a unique photoactivation through restructuring of the hydrogen-bonding network as opposed to a redox reaction or an isomerization of the chromophore. A conserved glutamine residue close to the flavin chromophore plays a central role in the light response, but the underlying modification is still unclear. We labelled this glutamine with 15N in two representative BLUF domains and performed time-resolved infrared double difference spectroscopy. The assignment of the signals was conducted by extensive quantum chemical calculations on large models with 187 atoms reproducing the UV-vis and infrared signatures of BLUF photoactivation. In the dark state, the comparatively low frequency of 1,667 cm−1 is assigned to the glutamine C=O accepting a hydrogen bond from tyrosine. In the light state, the signature of a tautomerised glutamine was extracted with the C=N stretch at ~1,691 cm−1 exhibiting the characteristic strong downshift by 15N labelling. Moreover, an indirect isotope effect on the flavin C4=O stretch was found. We conclude that photoactivation of the BLUF receptor does not only involve a rearrangement of hydrogen bonds but includes a change in covalent bonds of the protein.