H2O-Bridged Proton-Transfer Channel in Emitter Species Formation in Obelin Bioluminescence,The Journal of Physical Chemistry B

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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,

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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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