Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, China.
Photobiology Laboratory, Institute of Biophysics SB RAS, Federal Research Center "Krasnoyarsk Science Center SB RAS", Krasnoyarsk, Russia.
Photochem Photobiol. 2020 Sep;96(5):1047-1060. doi: 10.1111/php.13280. Epub 2020 Jun 24.
Calcium-regulated photoproteins are found in at least five phyla of organisms. The light emitted by those photoproteins can be tuned by mutating the photoprotein and/or by modifying the substrate coelenterazine (CTZ). Thirty years ago, Shimomura observed that the luminescence activity of aequorin was dramatically reduced when the substrate CTZ was replaced by its analog v-CTZ. The latter is formed by adding a phenyl ring to the π-conjugated moiety of CTZ. The decrease in luminescence activity has not been understood until now. In this paper, through combined quantum mechanics and molecular mechanics calculations as well as molecular dynamics simulations, we discovered the reason for this observation. Modification of the substrate changes the conformation of nearby aromatic residues and enhances the π-π stacking interactions between the conjugated moiety of v-CTZ and the residues, which weakens the charge transfer to form light emitter and leads to a lower luminescence activity. The microenvironments of CTZ in obelin and in aequorin are very similar, so we predicted that the luminescence activity of obelin will also dramatically decrease when CTZ is replaced by v-CTZ. This prediction has received strong evidence from currently theoretical calculations and has been verified by experiments.
钙调发光蛋白存在于至少五个生物门的生物中。通过突变发光蛋白和/或修饰其底物腔肠素（CTZ），可以调节这些发光蛋白发出的光。三十年前，Shimomura 观察到在将 CTZ 的底物替换为其类似物 v-CTZ 时，水母发光蛋白的发光活性显著降低。后者是通过在 CTZ 的 π-共轭部分上添加一个苯环形成的。直到现在，这种发光活性的降低还没有得到解释。在本文中，通过结合量子力学和分子力学计算以及分子动力学模拟，我们发现了这一观察结果的原因。底物的修饰改变了附近芳香族残基的构象，并增强了 v-CTZ 的共轭部分与残基之间的π-π堆积相互作用，这削弱了电荷转移以形成发光体，导致发光活性降低。Obelin 和水母发光蛋白中的 CTZ 微环境非常相似，因此我们预测当 CTZ 被 v-CTZ 取代时，Obelin 的发光活性也会显著降低。这一预测得到了目前理论计算的有力证据，并通过实验得到了验证。
