Atomistic Insights Into The Mechanism of Dual Affinity Switching In Plant Nitrate Transporter NRT1.1
Atomistic Insights Into The Mechanism of Dual Affinity Switching In Plant Nitrate Transporter NRT1.1
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DOI：
10.1101/2022.10.17.512638
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
Balaji Selvam;Jiangyan Feng;D. Shukla
中科院分区：
文献类型：
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作者：
Balaji Selvam;Jiangyan Feng;D. Shukla
提高氮肥利用效率对于提高农业生产力和减轻环境污染至关重要。为了克服土壤硝酸盐浓度的波动，植物进化出了一种复杂的硝酸盐运输机制，可以在高亲和力和低亲和力之间切换。在植物中，NRT1.1（一种与根相关的硝酸盐转运蛋白）在 Thr101 磷酸化后切换其亲和力。然而，这种被称为双亲和力转换的独特功能行为的分子基础仍然难以捉摸。 NRT1.1 硝酸盐转运蛋白的晶体结构为两个相互竞争的假设提供了证据，以解释双亲和力转换的起源。目前尚不清楚转运蛋白磷酸化和二聚化之间的相互作用如何调节亲和力转换。为了协调不同的假设，我们结合马尔可夫态模型对硝酸盐转运蛋白进行了广泛的模拟，以阐明双亲和力切换机制的分子起源。单体转运蛋白的模拟表明，磷酸化可稳定外向状态并加速动态转变以促进转运。另一方面，转运蛋白二聚体的磷酸化将二聚体的动态运动解耦成独立的单体，从而促进底物转运。因此，磷酸化诱导的底物运输增强和二聚体解偶联不仅协调了相互竞争的实验结果，而且还提供了植物中硝酸盐运输如何调节的原子论观点。
Improving nitrogen use efficiency is critical to enhancing agricultural productivity and to mitigate environmental pollution. To overcome the fluctuations in soil nitrate concentration, plants have evolved an elaborate nitrate transporting mechanism that switches between high and low affinity. In plants, NRT1.1, a root-associated nitrate transporter, switches its affinity upon phosphorylation at Thr101. However, the molecular basis of this unique functional behavior known as dual-affinity switching remains elusive. Crystal structures of the NRT1.1 nitrate transporter have provided evidence for the two competing hypotheses to explain the origin of dual-affinity switching. It is not known how the interplay between transporter phosphorylation and dimerization regulates the affinity switching. To reconcile the different hypotheses, we have performed extensive simulations of nitrate transporter in conjunction with Markov state models to elucidate the molecular origin for a dual-affinity switching mechanism. Simulations of monomeric transporter reveal that phosphorylation stabilizes the outward-facing state and accelerates dynamical transitions for facilitating transport. On the other hand, phosphorylation of the transporter dimer decouples dynamic motions of dimer into independent monomers and thus facilitates substrate transport. Therefore, the phosphorylation-induced enhancement of substrate transport and dimer decoupling not only reconcile the competing experimental results but also provide an atomistic view of how nitrate transport is regulated in plants.