小柯机器人

美国圣路易斯华盛顿大学Richard D. Vierstra、Van Andel研究所Huilin Li等研究人员合作发现，植物光敏素B（PhyB）是一种不对称的二聚体，并具有独特的信号潜力。2022年3月30日，《自然》杂志在线发表了这项成果。

研究人员报告了拟南芥PhyB在非活性Pr状态下的冷冻电镜结构，从而揭示了一个拓扑学上复杂的二聚体组织，它与原核生物的亲属有很大不同。C端组氨酸激酶相关结构（HKRD）不是预期的平行结构，而是头对头连接，而N端光敏区头对尾连接，形成一个平行四边形的平台，具有近两重对称性。该平台由两个内部Per/Arnt/Sim结构域中的第二个连接，该结构域与对立原聚体的光敏模块结合，前面的"调节器"环与自己原基的光敏模块紧密地结合。

这两种连接都加速了活性的Pfr向非活性的Pr的热还原，与二聚体组装和Pfr稳定性之间的反向关系相一致。HKRD和平台之间的片面接触为PhyB创造了深刻的不对称性，可能会给原聚体带来不同的信号潜力。研究人员提出，这种独特的结构动态为植物Phy光感受器及其信号伙伴之间的构象依赖性相互作用创造了一个广泛的光敏表面。

据介绍，植物光感觉的许多方面是由含bilin的光感受器家族的Phy介导的，这些光感受器在非活性的Pr和活性的Pfr构象体之间可逆地相互转换。尽管进行了广泛的生物化学研究，但由于缺乏相关的三维模型，对植物Phy信号的全面了解仍然不清楚。

附：英文原文

Title: Plant phytochrome B is an asymmetric dimer with unique signalling potential

Author: Li, Hua, Burgie, E. Sethe, Gannam, Zachary T. K., Li, Huilin, Vierstra, Richard D.

Issue&Volume: 2022-03-30

Abstract: Many aspects of plant photoperception are mediated by the phytochrome (Phy) family of bilin-containing photoreceptors that reversibly interconvert between inactive Pr and active Pfr conformers1,2. Despite extensive biochemical studies, full understanding of plant Phy signalling has remained unclear due to the absence of relevant 3D models. Here we report a cryo-electron microscopy structure of Arabidopsis PhyB in the Pr state that reveals a topologically complex dimeric organization that is substantially distinct from its prokaryotic relatives. Instead of an anticipated parallel architecture, the C-terminal histidine-kinase-related domains (HKRDs) associate head-to-head, whereas the N-terminal photosensory regions associate head-to-tail to form a parallelogram-shaped platform with near two-fold symmetry. The platform is internally linked by the second of two internal Per/Arnt/Sim domains that binds to the photosensory module of the opposing protomer and a preceding ‘modulator’ loop that assembles tightly with the photosensory module of its own protomer. Both connections accelerate the thermal reversion of Pfr back to Pr, consistent with an inverse relationship between dimer assembly and Pfr stability. Lopsided contacts between the HKRDs and the platform create profound asymmetry to PhyB that might imbue distinct signalling potentials to the protomers. We propose that this unique structural dynamism creates an extensive photostate-sensitive surface for conformation-dependent interactions between plant Phy photoreceptors and their signalling partners.

DOI: 10.1038/s41586-022-04529-z

Source: https://www.nature.com/articles/s41586-022-04529-z

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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