Molecular Mechanism of Spectral Tuning by Chloride Binding in Monkey Green Sensitive Visual Pigment
Molecular Mechanism of Spectral Tuning by Chloride Binding in Monkey Green Sensitive Visual Pigment
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DOI：
10.1021/acs.jpclett.2c03619
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发表时间：
2023-02-10
影响因子：
5.7
通讯作者：
Yanai，Takeshi
中科院分区：
文献类型：
--
作者：
Fujimoto，Kazuhiro J.;Minowa，Fumika;Yanai，Takeshi
视锥细胞的视觉色素可感知红色、绿色和蓝色。猴绿(MG)色素具有独特的氯离子结合部位；然而，它与绿色色素的光谱调谐之间的关系仍然难以捉摸。最近，傅里叶变换红外光谱分析揭示了氯离子结合对视网膜结合部位结构的影响。在此，我们报道了MG颜料的计算结构模型和量子化学模拟，以研究其光谱红移和存在氯离子时的物理化学相关性。我们的蛋白质结构反映了先前提出的结构变化。AlphaFold2未能预测到这些结构性变化。激发态计算成功地再现了实验中的红移吸收能，证实了我们的蛋白质结构。静电能量分解表明，红移是由His197质子化状态和Glu129、Ser202和Ala308的构象引起的，但氯离子本身对蓝移有贡献。定点突变支持我们的分析。这些模拟的结构可能为研究锥体颜料提供有价值的基础。
The visual pigments of the cones perceive red, green, and blue colors. The monkey green (MG) pigment possesses a unique Cl–binding site; however, its relationship to the spectral tuning in green pigments remains elusive. Recently, FTIR spectroscopy revealed the characteristic structural modifications of the retinal binding site by Cl–binding. Herein, we report the computational structural modeling of MG pigments and quantum-chemical simulation to investigate its spectral redshift and physicochemical relevance when Cl–is present. Our protein structures reflect the previously suggested structural changes. AlphaFold2 failed to predict these structural changes. Excited-state calculations successfully reproduced the experimental red-shifted absorption energies, corroborating our protein structures. Electrostatic energy decomposition revealed that the redshift results from the His197 protonation state and conformations of Glu129, Ser202, and Ala308; however, Cl–itself contributes to the blueshift. Site-directed mutagenesis supported our analysis. These modeled structures may provide a valuable foundation for studying cone pigments.