Nature2014-06-24 5:25 PM

多功能的硝酸盐转运机制 Molecular basis of nitrate uptake by the plant nitrate transporter NRT1.1

论文摘要 

土壤中的硝酸盐(植物生长的一种主要营养物)水平可以相差巨大。因此植物需要一个多功能机制来从环境中获取硝酸盐。在模型植物拟南芥中,双亲和性转运分子NRT1.1能吸收一系列不同浓度的硝酸盐,根据一个关键的苏氨酸残基的磷酸化状态从低亲和性模式向高亲和性模式切换。本期Nature上发表的两项研究描述了全长度NRT1.1的晶体结构,为了解这种转录后修饰怎样在低亲和性和高亲和性状态之间切换该转运分子提供了信息。

Abstract 

The NRT1/PTR family of proton-coupled transporters are responsible for nitrogen assimilation in eukaryotes and bacteria through the uptake of peptides. However, in most plant species members of this family have evolved to transport nitrate as well as additional secondary metabolites and hormones. In response to falling nitrate levels, NRT1.1 is phosphorylated on an intracellular threonine that switches the transporter from a low-affinity to high-affinity state. Here we present both the apo and nitrate-bound crystal structures of Arabidopsis thaliana NRT1.1, which together with in vitro binding and transport data identify a key role for His 356 in nitrate binding. Our data support a model whereby phosphorylation increases structural flexibility and in turn the rate of transport. Comparison with peptide transporters further reveals how the NRT1/PTR family has evolved to recognize diverse nitrogenous ligands, while maintaining elements of a conserved coupling mechanism within this superfamily of nutrient transporters.

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