Structure and mechanism of a nitrate transporter.
Structure and mechanism of a nitrate transporter.
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DOI：
10.1016/j.celrep.2013.03.007
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发表时间：
2013-03
期刊：
影响因子：
8.8
通讯作者：
Hanchi Yan;Weiyun Huang;Chuangye Yan;Xinqi Gong;Sirui Jiang;Yu Zhao;Jiawei Wang;Yigong Shi
中科院分区：
文献类型：
--
作者：
Hanchi Yan;Weiyun Huang;Chuangye Yan;Xinqi Gong;Sirui Jiang;Yu Zhao;Jiawei Wang;Yigong Shi
硝酸盐/亚硝酸盐转运蛋白NarK和NarU在细菌的氮稳态中起着重要作用，并且属于主要易化超家族（MFS）折叠的硝酸盐/亚硝酸盐转运蛋白家族（NNP）。NarK和NarU的结构和功能机制尚不清楚。在这里，我们报告的晶体结构的NarU在3.1毫米的分辨率和系统的生化表征。两个分子的NarU在一个不对称的单位表现出两种不同的构象状态：封闭和部分向内开放。底物分子硝酸盐似乎是由四个高度保守的，带电的或极性的氨基酸协调。结构和生化分析允许识别参与底物门控和转运的关键氨基酸。所观察到的构象差异的NarU，连同独特的序列特征的NNP家族转运蛋白，表明运输机制，可能偏离典型的摇杆开关模型。
The nitrate/nitrite transporters NarK and NarU play an important role in nitrogen homeostasis in bacteria and belong to the nitrate/nitrite porter family (NNP) of the major facilitator superfamily (MFS) fold. The structure and functional mechanism of NarK and NarU remain unknown. Here, we report the crystal structure of NarU at a resolution of 3.1 Å and systematic biochemical characterization. The two molecules of NarU in an asymmetric unit exhibit two distinct conformational states: occluded and partially inward-open. The substrate molecule nitrate appears to be coordinated by four highly conserved, charged, or polar amino acids. Structural and biochemical analyses allowed the identification of key amino acids that are involved in substrate gating and transport. The observed conformational differences of NarU, together with unique sequence features of the NNP family transporters, suggest a transport mechanism that might deviate from the canonical rocker-switch model.