Ionic Atmosphere Effect on the Absorption Spectrum of a Flavoprotein: A Reminder to Consider Solution Ions
Ionic Atmosphere Effect on the Absorption Spectrum of a Flavoprotein: A Reminder to Consider Solution Ions
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DOI：
10.1021/acs.jpclett.1c02173
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发表时间：
2021-08-26
影响因子：
5.7
通讯作者：
Gozem, Samer
中科院分区：
文献类型：
--
作者：
Dratch, Benjamin D.;Orozco-Gonzalez, Yoelvis;Gozem, Samer
本研究利用铜绿假单胞菌PAO1依赖于FMN的NADH：Q氧化还原酶，研究了在无和存在来自溶液离子的长程静电势的情况下，引入活性中心负电荷对黄素吸收光谱的影响。当活性中心酪氨酸(Y277)在体外去质子化时，黄素紫外可见光谱没有观察到变化。这些结果只能用包括正负溶液离子的平均溶剂静电组态(ASEC)QM/MM模拟来计算重现。用最少的离子中和总的蛋白质电荷进行的相同计算预测，去质子化Y277将显著改变黄素吸收光谱。对溶液离子分布的分析表明，Y277去质子化后，离子在蛋白质表面发生重组，抵消了酪氨酸对黄素吸收光谱的影响。为了验证这一假说，还进行了其他生化实验。
This study utilizes the FMN-dependent NADH:quinone oxidoreductase from Pseudomonas aeruginosa PAO1 to investigate the effect of introducing an active site negative charge on the flavin absorption spectrum both in the absence and presence of a long-range electrostatic potential coming from solution ions. There were no observed changes in the flavin UV-visible spectrum when an active site tyrosine (Y277) becomes deprotonated in vitro. These results could only be reproduced computationally using average solvent electrostatic configuration (ASEC) QM/MM simulations that include both positive and negative solution ions. The same calculations performed with minimal ions to neutralize the total protein charge predicted that deprotonating Y277 would significantly alter the flavin absorption spectrum. Analyzing the distribution of solution ions indicated that the ions reorganize around the protein surface upon Y277 deprotonation to cancel the effect of the tyrosinate on the flavin absorption spectrum. Additional biochemical experiments were performed to test this hypothesis.