A cytosolic trans-activation domain essential for ammonium uptake
A cytosolic trans-activation domain essential for ammonium uptake
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DOI：
10.1038/nature05579
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发表时间：
2007-03-08
期刊：
影响因子：
64.8
通讯作者：
Frommer, W. B.
中科院分区：
文献类型：
--
作者：
Loque, D.;Lalonde, S.;Frommer, W. B.
多位膜蛋白对于细胞摄取和释放营养物质至关重要。为了防止有毒物质积累，需要快速关闭机制。在这里，我们展示了来自拟南芥的寡聚铵转运蛋白的可溶性胞质羧基末端作为功能所必需的变构调节剂。细菌、真菌和植物之间保守的 C 端结构域发生突变，导致转运活性丧失。当与完整转运蛋白共表达时，突变体使功能亚基失活，但其稳定性不受影响。两种无活性转运蛋白（一种具有缺陷孔，另一种具有被消融的 C 末端）的共表达，重建了活性。古生球菌铵转运蛋白 (AMT)(1) 的晶体结构表明 C 末端与邻近亚基的胞质环发生物理相互作用。 C 末端保守位点的磷酸化 (2) 被认为是同源控制机制。单体之间的构象耦合提供了一种严格调节的机制，用于增加感知和记忆先前事件的动态范围，并且可能是转运蛋白调节的通用机制。
Polytopic membrane proteins are essential for cellular uptake and release of nutrients. To prevent toxic accumulation, rapid shut-off mechanisms are required. Here we show that the soluble cytosolic carboxy terminus of an oligomeric ammonium transporter from Arabidopsis thaliana serves as an allosteric regulator essential for function; mutations in the C-terminal domain, conserved between bacteria, fungi and plants, led to loss of transport activity. When co-expressed with intact transporters, mutants inactivated functional subunits, but left their stability unaffected. Co-expression of two inactive transporters, one with a defective pore, the other with an ablated C terminus, reconstituted activity. The crystal structure of an Archaeoglobus fulgidus ammonium transporter (AMT)(1) suggests that the C terminus interacts physically with cytosolic loops of the neighbouring subunit. Phosphorylation of conserved sites in the C terminus(2) are proposed as the cognate control mechanism. Conformational coupling between monomers provides a mechanism for tight regulation, for increasing the dynamic range of sensing and memorizing prior events, and may be a general mechanism for transporter regulation.