On the Role of the Conserved Histidine at the Chromophore Isomerization Site in Phytochromes.
On the Role of the Conserved Histidine at the Chromophore Isomerization Site in Phytochromes.
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DOI：
10.1021/acs.jpcb.1c08245
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发表时间：
2021-12-23
影响因子：
3.3
通讯作者：
Hildebrandt, Peter
中科院分区：
文献类型：
--
作者：
Kraskov, Anastasia;Buhrke, David;Scheerer, Patrick;Shaef, Ida;Sanchez, Juan C.;Carrillo, Melissa;Noda, Moraima;Feliz, Denisse;Stojkovic, Emina A.;Hildebrandt, Peter
光敏色素是感觉光感受器，利用光驱动蛋白质结构变化，进而引发生理反应级联。该过程从光传感核心模块中线性次甲基桥联四吡咯发色团的双键光异构化开始。光转换的分子机制取决于发色团环境的结构和静电特性，这些特性在相关光敏色素中高度保守。然而，单个氨基酸的具体作用尚不清楚。异构化位点附近的组氨酸在所有光敏色素中高度保守且几乎不变。本研究旨在通过利用来自橙色臭霉的粘细菌光敏色素 SaBphP1 来分析其作用，其中组氨酸天然被苏氨酸 (Thr289) 取代，并将其与来自同一生物体 SaBphP2 (His275) 的正常含组氨酸对应物进行比较。我们使用来自农杆菌的良好表征的原型光敏色素 Agp1 作为参考，对野生型蛋白质及其各自的组氨酸或苏氨酸取代变体（SaBphP1-T289H 和 SaBphP2-H275T）进行了详细的共振拉曼和红外光谱研究。光转换的整体机制对组氨酸取代不敏感。然而，异构化位点的发色团几何形状似乎受到影响，在 Thr 存在下，D 环的扭曲稍强，这足以导致 SaBphP1 和 SaBphP2 中不同的光吸收特性。此外，His 的存在允许与 D 环羰基发生多重氢键相互作用，这可能是 C-D 次甲基桥与含 Thr 变体相比几何差异的根源。其他结构和机制上的差异与他的存在无关。最引人注目的发现是 SaBphP2 的 Pfr 状态下 C 环丙酸酯的质子化，这在深海光敏色素中很常见，但迄今为止在原型光敏色素中尚未有报道。
Phytochromes are sensory photoreceptors that use light to drive protein structural changes, which in turn trigger physiological reaction cascades. The process starts with a double-bond photoisomerization of the linear methine-bridged tetrapyrrole chromophore in the photosensory core module. The molecular mechanism of the photoconversion depends on the structural and electrostatic properties of the chromophore environment, which are highly conserved in related phytochromes. However, the specific role of individual amino acids is yet not clear. A histidine in the vicinity of the isomerization site is highly conserved and almost invariant among all phytochromes. The present study aimed at analyzing its role by taking advantage of a myxobacterial phytochrome SaBphP1 from Stigmatella aurantiaca, where this histidine is naturally substituted with a threonine (Thr289), and comparing it to its normal, His-containing counterpart from the same organism SaBphP2 (His275). We have carried out a detailed resonance Raman and IR spectroscopic investigation of the wild-type proteins and their respective His- or Thr-substituted variants (SaBphP1-T289H and SaBphP2-H275T) using the well-characterized prototypical phytochrome Agp1 from Agrobacterium fabrum as a reference. The overall mechanism of the photoconversion is insensitive toward the His substitution. However, the chromophore geometry at the isomerization site appears to be affected, with a slightly stronger twist of ring D in the presence of Thr, which is sufficient to cause different light absorption properties in SaBphP1 and SaBphP2. Furthermore, the presence of His allows for multiple hydrogen-bonding interactions with the ring D carbonyl which may be the origin for the geometric differences of the C–D methine bridge compared to the Thr-containing variants. Other structural and mechanistic differences are independent of the presence of His. The most striking finding is the protonation of the ring C propionate in the Pfr states of SaBphP2, which is common among bathy phytochromes but so far has not been reported in prototypical phytochromes.
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影响因子：
21.8
作者：
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通讯作者：
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影响因子：
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