Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany.
Leloir Institute Foundation, IIBBA-CONICET, Av. Patricias Argentinas 435 (C1405BWE), Buenos Aires, Argentina.
Phys Chem Chem Phys. 2022 May 18;24(19):11967-11978. doi: 10.1039/d2cp00020b.
Phytochromes, found in plants, fungi, and bacteria, exploit light as a source of information to control physiological processes photoswitching between two states of different physiological activity, a red-absorbing Pr and a far-red-absorbing Pfr state. Depending on the relative stability in the dark, bacterial phytochromes are divided into prototypical and bathy phytochromes, where the stable state is Pr and Pfr, respectively. In this work we studied representatives of these groups (prototypical Agp1 and bathy Agp2 from ) together with the bathy-like phytochrome BphP from by resonance Raman and IR difference spectroscopy. In all three phytochromes, the photoinduced conversions display the same mechanistic pattern as reflected by the chromophore structures in the various intermediate states. We also observed in each case the secondary structure transition of the tongue, which is presumably crucial for the function of phytochrome. The three phytochromes differ in details of the chromophore conformation in the various intermediates and the energetic barrier of their respective decay reactions. The specific protein environment in the chromophore pocket, which is most likely the origin for these small differences, also controls the proton transfer processes concomitant to the photoconversions. These proton translocations, which are tightly coupled to the structural transition of the tongue, presumably proceed the same mechanism along the Pr → Pfr conversion whereas the reverse Pfr → Pr photoconversion includes different proton transfer pathways. Finally, classification of phytochromes in prototypical and bathy (or bathy-like) phytochromes is discussed in terms of molecular structure and mechanistic properties.
植物、真菌和细菌中的光受体（phytochromes）利用光作为信息源来控制生理过程——在两种具有不同生理活性的状态之间进行光致开关转换，这两种状态分别是红光吸收的 Pr 和远红光吸收的 Pfr。根据在黑暗中的相对稳定性，细菌光受体可分为原型和深海光受体，其中稳定状态分别为 Pr 和 Pfr。在这项工作中，我们通过共振拉曼和 IR 差谱研究了这两个组别的代表（原型 Agp1 和深海 Agp2 来自 ，以及深海样光受体 BphP 来自 ）。在所有三种光受体中，光诱导转换显示出相同的机制模式，这反映在各种中间状态的发色团结构中。我们还在每种情况下观察到舌的二级结构转换，这对于光受体的功能可能至关重要。这三种光受体在各种中间态中发色团构象的细节以及各自衰减反应的能垒上存在差异。发色团口袋中特定的蛋白质环境，很可能是这些小差异的起源，也控制着伴随光转换的质子转移过程。这些质子迁移与舌的结构转换紧密耦合，推测沿着 Pr → Pfr 转换以相同的机制进行，而反向的 Pfr → Pr 光转换包括不同的质子转移途径。最后，根据分子结构和机制特性，讨论了将光受体分为原型和深海（或深海样）光受体的分类。
