Plant phytochrome B is an asymmetric dimer with unique signalling potential.
Plant phytochrome B is an asymmetric dimer with unique signalling potential.
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DOI：
10.1038/s41586-022-04529-z
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发表时间：
2022-04
期刊：
影响因子：
64.8
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中科院分区：
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植物光感受的许多方面是由光敏色素（Phy）家族介导的含胆色素的光感受器，其在非活性Pr和活性Pfr构象异构体之间可逆地相互转化。尽管进行了广泛的生物化学研究，但由于缺乏相关的3D模型，对植物Phy信号传导的充分理解仍然不清楚。在这里，我们报告的冷冻电子显微镜结构的拟南芥PhyB在Pr状态，揭示了一个拓扑结构复杂的二聚体组织，是从它的原核亲属基本上不同。而不是一个预期的平行架构，C-末端组氨酸激酶相关结构域（HKRDs）关联头对头，而N-末端感光区关联头到尾，形成一个平行四边形的平台与近两倍对称。该平台由两个内部Per/Arnt/Sim结构域中的第二个内部连接，该结构域结合到相对原聚体的感光模块和与其自身原聚体的感光模块紧密组装的前一个“调节剂”环。这两种连接加速PFR的热回复到Pr，与二聚体组装和PFR稳定性之间的反比关系一致。HKRDs和平台之间的不平衡接触对PhyB产生了深刻的不对称性，这可能会给原聚体带来不同的信号传导潜力。我们建议，这种独特的结构动力学创建一个广泛的光敏感表面的植物Phy光受体和它们的信号合作伙伴之间的构象依赖的相互作用。
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 conformers. 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.
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DOI：
10.1074/jbc.ra118.003069
发表时间：
2018-06-08
期刊：
The Journal of biological chemistry
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