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Local Electric Field Changes during the Photoconversion of the Bathy Phytochrome Agp2
Biochemistry ( IF 2.9 ) Pub Date : 2021-09-27 , DOI: 10.1021/acs.biochem.1c00426 Anastasia Kraskov 1 , Johannes von Sass 1 , Anh Duc Nguyen 1 , Tu Oanh Hoang 1 , David Buhrke 1 , Sagie Katz 1 , Norbert Michael 1 , Jacek Kozuch 2 , Ingo Zebger 1 , Friedrich Siebert 3 , Patrick Scheerer 4 , Maria Andrea Mroginski 1 , Nediljko Budisa 5 , Peter Hildebrandt 1
Biochemistry ( IF 2.9 ) Pub Date : 2021-09-27 , DOI: 10.1021/acs.biochem.1c00426 Anastasia Kraskov 1 , Johannes von Sass 1 , Anh Duc Nguyen 1 , Tu Oanh Hoang 1 , David Buhrke 1 , Sagie Katz 1 , Norbert Michael 1 , Jacek Kozuch 2 , Ingo Zebger 1 , Friedrich Siebert 3 , Patrick Scheerer 4 , Maria Andrea Mroginski 1 , Nediljko Budisa 5 , Peter Hildebrandt 1
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Phytochromes switch between a physiologically inactive and active state via a light-induced reaction cascade, which is initiated by isomerization of the tetrapyrrole chromophore and leads to the functionally relevant secondary structure transition of a protein segment (tongue). Although details of the underlying cause–effect relationships are not known, electrostatic fields are likely to play a crucial role in coupling chromophores and protein structural changes. Here, we studied local electric field changes during the photoconversion of the dark state Pfr to the photoactivated state Pr of the bathy phytochrome Agp2. Substituting Tyr165 and Phe192 in the chromophore pocket by para-cyanophenylalanine (pCNF), we monitored the respective nitrile stretching modes in the various states of photoconversion (vibrational Stark effect). Resonance Raman and IR spectroscopic analyses revealed that both pCNF-substituted variants undergo the same photoinduced structural changes as wild-type Agp2. Based on a structural model for the Pfr state of F192pCNF, a molecular mechanical–quantum mechanical approach was employed to calculate the electric field at the nitrile group and the respective stretching frequency, in excellent agreement with the experiment. These calculations serve as a reference for determining the electric field changes in the photoinduced states of F192pCNF. Unlike F192pCNF, the nitrile group in Y165pCNF is strongly hydrogen bonded such that the theoretical approach is not applicable. However, in both variants, the largest changes of the nitrile stretching modes occur in the last step of the photoconversion, supporting the view that the proton-coupled restructuring of the tongue is accompanied by a change of the electric field.
中文翻译：
浅海光敏色素 Agp2 光转换过程中的局部电场变化
光敏色素通过光诱导反应级联在生理失活和活性状态之间切换，该反应由四吡咯发色团的异构化引发，并导致蛋白质片段（舌）的功能相关二级结构转变。虽然潜在因果关系的细节尚不清楚，但静电场可能在耦合发色团和蛋白质结构变化中发挥关键作用。在这里，我们研究了在暗态 Pfr 到深光敏色素 Agp2 的光活化态 Pr 的光转换过程中局部电场的变化。将发色团口袋中的 Tyr165 和 Phe192 替换为para-氰基苯丙氨酸（pCNF），我们监测了各种光转换状态（振动斯塔克效应）下各自的腈拉伸模式。共振拉曼和红外光谱分析表明，两种 pCNF 取代的变体都经历了与野生型 Agp2 相同的光诱导结构变化。基于 F192pCNF 的 Pfr 状态的结构模型，采用分子力学 - 量子力学方法计算腈基的电场和相应的拉伸频率，与实验非常吻合。这些计算可作为确定 F192pCNF 光致状态中电场变化的参考。与 F192pCNF 不同，Y165pCNF 中的腈基是强氢键，因此理论方法不适用。然而，在这两种变体中，
更新日期：2021-10-12
中文翻译：
浅海光敏色素 Agp2 光转换过程中的局部电场变化
光敏色素通过光诱导反应级联在生理失活和活性状态之间切换，该反应由四吡咯发色团的异构化引发，并导致蛋白质片段（舌）的功能相关二级结构转变。虽然潜在因果关系的细节尚不清楚，但静电场可能在耦合发色团和蛋白质结构变化中发挥关键作用。在这里，我们研究了在暗态 Pfr 到深光敏色素 Agp2 的光活化态 Pr 的光转换过程中局部电场的变化。将发色团口袋中的 Tyr165 和 Phe192 替换为para-氰基苯丙氨酸（pCNF），我们监测了各种光转换状态（振动斯塔克效应）下各自的腈拉伸模式。共振拉曼和红外光谱分析表明，两种 pCNF 取代的变体都经历了与野生型 Agp2 相同的光诱导结构变化。基于 F192pCNF 的 Pfr 状态的结构模型，采用分子力学 - 量子力学方法计算腈基的电场和相应的拉伸频率，与实验非常吻合。这些计算可作为确定 F192pCNF 光致状态中电场变化的参考。与 F192pCNF 不同，Y165pCNF 中的腈基是强氢键，因此理论方法不适用。然而，在这两种变体中，
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