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H2O-Bridged Proton-Transfer Channel in Emitter Species Formation in Obelin Bioluminescence
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2021-09-14 , DOI: 10.1021/acs.jpcb.1c03985
Shu-Feng Chen 1 , Eugene S Vysotski 2 , Ya-Jun Liu 3, 4
Affiliation  

Bioluminescence of a number of marine organisms is conditioned by Ca2+-regulated photoprotein (CaRP) with coelenterazine as the reaction substrate. The reaction product, coelenteramide, at the first singlet excited state (S1) is the emitter of CaRP. The S1-state coelenteramide is produced via the decomposition of coelenterazine dioxetanone. Experiments suggested that the neutral S1-coelenteramide is the primary emitter species. This supposition contradicts with theoretical calculations showing that the anionic S1-coelenteramide is a primary product of the decomposition of coelenterazine dioxetanone. In this study, applying molecular dynamic (MD) simulations and the hybrid quantum mechanics/molecular mechanics (QM/MM) method, we investigated a proton-transfer (PT) process taking place in CaRP obelin from Obelia longissima for emitter formation. Our calculations demonstrate a concerted PT process with a water molecule as a bridge between anionic S1-coelenteramide and the nearest histidine residue. The low activation barrier as well as the strong hydrogen-bond network between the proton donor and the proton acceptor suggests a fast PT process comparable with that of the lifetime of excited anionic S1-coelenteramide. The existence of the PT process eliminates the discrepancy between experimental and theoretical studies. The fast PT process at emitter formation can also take place in other CaRPs.

中文翻译:

Obelin 生物发光中发射体物种形成中的 H2O 桥接质子转移通道

许多海洋生物的生物发光由 Ca 2+调节的光蛋白 (CaRP) 调节,腔肠素作为反应底物。反应产物腔肠酰胺处于第一个单线激发态 (S 1 ) 是 CaRP 的发射体。S 1 态腔肠酰胺是通过腔肠素二氧杂环丁酮的分解产生的。实验表明中性S 1 -腔肠酰胺是主要的发射体。这个假设与理论计算相矛盾,理论计算表明阴离子 S 1-腔肠酰胺是腔肠素二氧杂环丁酮分解的主要产物。在这项研究中,我们应用分子动力学 (MD) 模拟和混合量子力学/分子力学 (QM/MM) 方法,研究了在来自Obelia longissima 的CaRP obelin 中发生的质子转移 (PT) 过程,以形成发射极。我们的计算证明了协同 PT 过程,其中水分子作为阴离子 S 1 -腔肠酰胺和最近的组氨酸残基之间的桥梁。质子供体和质子受体之间的低激活势垒以及强氢键网络表明,快速 PT 过程与激发的阴离子 S 1的寿命相当-腔肠酰胺。PT 过程的存在消除了实验和理论研究之间的差异。发射极形成时的快速 PT 过程也可以发生在其他 CaRP 中。
更新日期:2021-09-23
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