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Molecular Mechanism of Brassinosteroid Perception by the Plant Growth Receptor BRI1.
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-01-07 , DOI: 10.1021/acs.jpcb.9b09377
Faisal Aldukhi , Aniket Deb 1 , Chuankai Zhao , Alexander S Moffett , Diwakar Shukla 2
Affiliation  

Brassinosteroids (BRs) are essential phytohormones, which bind to the plant receptor, BRI1, to regulate various physiological processes. The molecular mechanism of the perception of BRs by the ectodomain of BRI1 remains not fully understood. It also remains elusive why a substantial difference in biological activity exists between the BRs. In this work, we study the binding mechanisms of the two most bioactive BRs, brassinolide (BLD) and castasterone (CAT), using molecular dynamics simulations. We report free-energy landscapes of the binding processes of both ligands, as well as detailed ligand binding pathways. Our results suggest that CAT has a lower binding affinity compared to BLD due to its inability to form hydrogen-bonding interactions with a tyrosine residue in the island domain of BRI1. We uncover a conserved nonproductive binding state for both BLD and CAT, which is more stable for CAT and may further contribute to the bioactivity difference. Finally, we validate past observations about the conformational restructuring and ordering of the island domain upon BLD binding. Overall, this study provides new insights into the fundamental mechanism of the perception of the two most bioactive BRs, which may create new avenues for genetic and agrochemical control of their signaling cascade.

中文翻译:

植物生长受体BRI1对油菜素类固醇感知的分子机理。

油菜素类固醇(BRs)是必需的植物激素,它与植物受体BRI1结合以调节各种生理过程。BRI1的胞外域对BRs的感知的分子机制仍不完全清楚。还不清楚为什么BR之间存在生物学活性上的实质性差异。在这项工作中,我们使用分子动力学模拟研究了两种生物活性最高的BRs,油菜素内酯(BLD)和Castasterone(CAT)的结合机理。我们报告了两个配体的结合过程,以及详细的配体结合途径的自由能景观。我们的结果表明,与BLD相比,CAT具有较低的结合亲和力,因为它无法与BRI1岛结构域中的酪氨酸残基形成氢键相互作用。我们发现BLD和CAT的保守的非生产性结合状态,这对于CAT更稳定,并可能进一步导致生物活性差异。最后,我们验证了过去有关BLD结合时岛结构域构象重组和有序排列的观察结果。总的来说,这项研究提供了对两种生物活性最高的BRs感知的基本机制的新见解,这可能为遗传和农用化学控制它们的信号传导级联开辟新途径。
更新日期:2020-01-07
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