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首页> 外文期刊>Biochemistry >Protonation state and structural changes of the tetrapyrrole chromophore during the Pr --> Pfr phototransformation of phytochrome: a resonance Raman spectroscopic study.
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Protonation state and structural changes of the tetrapyrrole chromophore during the Pr --> Pfr phototransformation of phytochrome: a resonance Raman spectroscopic study.

机译：植物色素Pr-> Pfr光转化过程中四吡咯发色团的质子化状态和结构变化：共振拉曼光谱研究。

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    The photoconversion of phytochrome (phytochrome A from Avena satina) from the inactive (Pr) to the physiologically active form (Pfr) was studied by near-infrared Fourier transform resonance Raman spectroscopy at cryogenic temperatures, which allow us to trap the intermediate states. Nondeuterated and deuterated buffer solutions were used to determine the effect of H/D exchange on the resonance Raman spectra. For the first time, reliable spectra of the "bleached" intermediates meta-R(A) and meta-R(C) were obtained. The vibrational bands in the region 1300-1700 cm(-)(1), which is particularly indicative of structural changes in tetrapyrroles, were assigned on the basis of recent calculations of the Raman spectra of the chromophore in C-phycocyanin and model compounds [Kneip, C., Hildebrandt, P., Nemeth, K., Mark, F., Schaffner, K. (1999) Chem. Phys. Lett. 311, 479-485]. The experimental resonance Raman spectra Pr are compatible with the Raman spectra calculated for the protonated ZZZasa configuration, which hence is suggested to be the chromophore structure in this parent state of phytochrome. Furthermore, marker bands could be identified that are of high diagnostic value for monitoring structural changes in individual parts of the chromophore. Specifically, it could be shown that not only in the parent states Pr and Pfr but also in all intermediates the chromophore is protonated at the pyrroleninic nitrogen. The spectral changes observed for lumi-R confirm the view that the photoreaction of Pr is a Z --> E isomerization of the CD methine bridge. The subsequent thermal decay reaction to meta-R(A) includes relaxations of the CD methine bridge double bond, whereas the formation of meta-R(C) is accompanied by structural adaptations of the pyrrole rings B and C in the protein pocket. The far-reaching similarities between the chromophores of meta-R(A) and Pfr suggest that in the step meta-R(A) --> Pfr the ultimate structural changes of the protein matrix occur.
    机译：通过在低温下进行近红外傅里叶变换共振拉曼光谱研究了植物色素（来自Avena satina的植物色素A）从非活性形式（Pr）到生理活性形式（Pfr）的光转换，这使我们能够捕获中间状态。使用非氘代和氘代缓冲溶液确定H / D交换对共振拉曼光谱的影响。首次获得“漂白”中间体meta-R（A）和meta-R（C）的可靠光谱。根据最近对C-藻蓝蛋白和模型化合物中发色团的拉曼光谱的计算结果，分配了1300-1700 cm（-）（1）区域的振动带，该振动带特别表明四吡咯的结构变化。 Kneip，C.，Hildebrandt，P.，Nemeth，K.，Mark，F.，Schaffner，K.（1999）Chem。物理来吧311，479-485]。实验共振拉曼光谱Pr与为质子化的ZZZasa构型计算的拉曼光谱兼容，因此被认为是在此植物色素母体状态下的发色团结构。此外，可以识别出具有高诊断价值的标记带，用于监测生色团各个部分的结构变化。具体地，可以表明，不仅在母体状态Pr和Pfr中，而且在所有中间体中，发色团在吡咯烯基氮处质子化。对于lumi-R观察到的光谱变化证实了这样的观点，即Pr的光反应是CD次甲基桥的Z-> E异构化。随后对meta-R（A）的热衰变反应包括CD次甲基桥双键的松弛，而meta-R（C）的形成伴随着蛋白质口袋中吡咯环B和C的结构适应。 meta-R（A）和Pfr的发色团之间的深远相似性表明，在meta-R（A）-> Pfr步骤中，蛋白质基质的最终结构发生了变化。

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