The Lumi-R Intermediates of Prototypical Phytochromes
The Lumi-R Intermediates of Prototypical Phytochromes
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DOI：
10.1021/acs.jpcb.0c01059
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发表时间：
2020-05-21
影响因子：
3.3
通讯作者：
Hildebrandt, Peter
中科院分区：
文献类型：
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作者：
Escobar, Francisco Velazquez;Kneip, Christa;Hildebrandt, Peter
光敏色素是一种光感受器，光吸收后会引发一系列生理反应。起始点是四吡咯辅因子在母体Pr状态下的光异构化，随后是热松弛步骤，最终激活生理信号。在这里，我们使用共振拉曼光谱(RR)研究了初级光产物Lumi-R的生色团结构，捕获温度在130-200K之间。研究范围包括植物(PhyA)和原核生物(Cph1、Agp1、CphB和RpBphP2)的光致变色蛋白，包括光敏变色剂(P Phi B)、藻蓝胆素(PCb)和胆绿素(BV)。在P Phi B和PCb结合的PhyA和Cph1中，根据顺序和平行反应模型识别和讨论了两种Lumi-R状态(Lumi-R1，Lumi-R2)。在Lumi-R1中，发色团的结构变化仅限于C-D亚甲基桥异构化位置，但在Lumi-R2中，发色团的结构变化贯穿整个发色团。形成和衰减动力学以及光化学活性取决于特定的蛋白质-发色团相互作用，从而解释了Lumi-RL和Lumi-R2在不同的P-Phi B(多氯联苯)结合的光敏色素的光固定混合物中的不同分布。对于BV结合的细菌光敏色素，只有一种Lumi-R(BV)状态。在这种状态下，AGP 1、CphB和RpBphP2类似，生色团的结构变化包括C-D亚甲基桥的主要扭转，但也包括远离异构化中心的A-B亚甲基桥的扰动。P-Phi B(PCB)结合的光敏色素和副结合的细菌光敏色素的不同结构归因于D环在异构化过程中的不同配置，这导致了这两类光敏色素在Lumi-R状态下不同的蛋白质-发色团相互作用。
Phytochromes are photoreceptors that upon light absorption initiate a physiological reaction cascade. The starting point is the photoisomerization of the tetrapyrrole cofactor in the parent Pr state, followed by thermal relaxation steps culminating in activation of the physiological signal. Here we have employed resonance Raman (RR) spectroscopy to study the chromophore structure in the primary photoproduct Lumi-R, trapped between 130 and 200 K. The investigations covered phytochromes from plants (phyA) and prokaryotes (Cph1, Agp1, CphB, and RpBphP2) including phytochromobilin (P Phi B), phycocyanobilin (PCB), and biliverdin (BV). In P Phi B- and PCB-binding phyA and Cph1, two Lumi-R states (Lumi-R1, Lumi-R2) were identified and discussed in terms of sequential and parallel reaction models. In Lumi-R1, the chromophore structural changes are restricted to the C-D methine bridge isomerization site but extended throughout the chromophore in Lumi-R2. Formation and decay kinetics as well as photochemical activity depend on the specific protein-chromophore interactions and thus account for the different distribution between Lumi-Rl and Lumi-R2 in the photostationary mixtures of the various P Phi B(PCB)-binding phytochromes. For BV-binding bacteriophytochromes, only a single Lumi-R(BV) state was found. In this state, which is similar for Agp 1, CphB, and RpBphP2, the chromophore structural changes comprise major torsions of the C-D methine bridge but also perturbations at the A-B methine bridge remote from the isomerization site. The different structures of the photoproducts in P Phi B(PCB)-binding phytochromes and By-binding bacteriophytochromes are attributed to the different disposition of ring D upon isomerization, which leads to distinct protein-chromophore interactions in the Lumi-R states of these two classes of phytochromes.