Common Structural Elements in the Chromophore Binding Pocket of the Pfr State of Bathy Phytochromes
Common Structural Elements in the Chromophore Binding Pocket of the Pfr State of Bathy Phytochromes
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DOI：
10.1111/php.12742
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发表时间：
2017-05-01
影响因子：
3.3
通讯作者：
Hildebrandt, Peter
中科院分区：
文献类型：
--
作者：
Escobar, Francisco Velazquez;Buhrke, David;Hildebrandt, Peter
光敏色素是双峰光感受器，其在被四吡咯发色团吸收光时可以在红色吸收态（Pr）和远红色吸收态（Pfr）之间转换。在细菌光敏色素中，Pr或Pfr是热稳定状态，从而分别构成原型光敏色素和bathy光敏色素的类别。在这项工作中，我们已经采用振动光谱来阐明的起源的Pfr态的热稳定性的bathy光敏色素。在这里，我们提出了RpBphP 6的第一个详细的光谱分析（沼泽红球藻），其与针对Agp 2获得的结果一起（根癌农杆菌）和PaBphP（铜绿假单胞菌）允许鉴定碱性光敏色素的Pfr状态的共同结构特性，其是（1）均质发色团结构，（2）发色团的质子化的C环丙酸侧链和（3）在D环氮处的延迟的H/D交换。这些性质与环D N-H基团与保守Asp 194（PaBphP编号）侧链之间的氢键相互作用的独特强度有关。正如所揭示的同源性模型和可用的晶体结构的PFR状态的比较分析，这些相互作用的加强由一个精氨酸残基（Arg 453），只有在洗澡，但不是在原型光敏色素。
Phytochromes are bimodal photoreceptors which, upon light absorption by the tetrapyrrole chromophore, can be converted between a red-absorbing state (Pr) and far-red-absorbing state (Pfr). In bacterial phytochromes, either Pr or Pfr are the thermally stable states, thereby constituting the classes of prototypical and bathy phytochromes, respectively. In this work, we have employed vibrational spectroscopies to elucidate the origin of the thermal stability of the Pfr states in bathy phytochromes. Here, we present the first detailed spectroscopic analysis of RpBphP6 (Rhodopseudomas palustris), which together with results obtained for Agp2 (Agrobacterium tumefaciens) and PaBphP (Pseudomonas aeruginosa) allows identifying common structural properties of the Pfr state of bathy phytochromes, which are (1) a homogenous chromophore structure, (2) the protonated ring C propionic side chain of the chromophore and (3) a retarded H/D exchange at the ring D nitrogen. These properties are related to the unique strength of the hydrogen bonding interactions between the ring D N-H group with the side chain of the conserved Asp194 (PaBphP numbering). As revealed by a comparative analysis of homology models and available crystal structures of Pfr states, these interactions are strengthened by an Arg residue (Arg453) only in bathy but not in prototypical phytochromes.