Dual Photochemical Reaction Pathway in Flavin-Based Photoreceptor LOV Domain: A Combined Quantum-Mechanics/Molecular-Mechanics Investigation
Dual Photochemical Reaction Pathway in Flavin-Based Photoreceptor LOV Domain: A Combined Quantum-Mechanics/Molecular-Mechanics Investigation
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基于黄素的光感受器 LOV 结构域中的双重光化学反应途径：量子力学/分子力学相结合的研究
DOI：
10.1021/acs.jpcb.7b09207
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Marian Christel M.
中科院分区：
文献类型：
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作者：
Nakagawa Setsuko;Weingart Oliver;Marian Christel M.
采用高水平QM（DFT/MRCI）/MM方法研究了枯草芽孢杆菌蓝光光敏元件YtvA的光、氧和电压（LOV）结构域的初级光化学反应。在蓝光激发下，活性半胱氨酸的Sγ原子与黄素单核苷酸（FMN）环的C4 a形成共价键。在YtvA-LOV的X射线晶体学结构中观察到反应性半胱氨酸侧链的两种构象，占有率为70%（配置A）和30%（配置B）（Möglich，A.; Moffat，K. J. Mol. 2007，373，112 - 126）。在结构A中，硫醇基团指向FMN环的二甲苯部分，而在结构B中，硫醇基团直接位于FMN环的N5原子上方。从这两种构象开始，单重态和三重态激发途径进行了评价。从conf A激发的单重态通过系间跃迁（ISC）非辐射地衰减到三重态。在中性双自由基形成后，三重态通过第二ISC交叉到电子基态，并且有效地形成加合物。从conf B激发的单重态位于S1/S 0锥形交叉点（CIn）附近。大部分通过CIn返回到初始状态。其余的可以直接达到加合物状态。因此，光激发具有双重反应途径。在YtvA-LOV中，推断通过绕过来自conf B的效率较低的单重激发来选择来自conf A的有效三重激发。
The primary photochemical reaction of the light, oxygen, and voltage (LOV) domain of the blue-light photosensor YtvA ofBacillus subtiliswere investigated using high-level QM(DFT/MRCI)/MM methods. After blue-light excitation, the Sγatom of the reactive cysteine forms a covalent bond with the C4aof the flavin mononucleotide (FMN) ring. Two conformations for the side chain of reactive cysteine with occupancies of 70% (conf A) and 30% (conf B) are observed in the X-ray crystallographic structures of the YtvA-LOV (Möglich, A.; Moffat, K. J. Mol. Biol. 2007, 373, 112−126). In conf A, the thiol group is directed toward the dimethylbenzene moiety of the FMN ring whereas it is placed directly above the N5atom of the FMN ring in conf B. Starting from both conformations, the singlet and triplet excited pathways were evaluated. The singlet states excited from conf A decay nonradiatively to the triplet states by intersystem crossing (ISC). After the formation of a neutral biradical, the triplet states cross over to the electronic ground state by a second ISC and the adducts are efficiently formed. The singlet states excited from conf B are located near the S1/S0conical intersection (CIn). A major fraction returns to the initial states through the CIn. The rest may directly reach the adduct state. Thus, the photoexcitation has a dual reaction pathway. In YtvA-LOV, it is inferred that the efficient triplet excitation from conf A was chosen by bypassing the less efficient singlet excitation from conf B.