Crystal structure of the CorA Mg2+ transporter
Crystal structure of the CorA Mg2+ transporter
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DOI：
10.1038/nature04642
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发表时间：
2006-04-06
期刊：
影响因子：
64.8
通讯作者：
Koth, CM
中科院分区：
文献类型：
--
作者：
Lunin, VV;Dobrovetsky, E;Koth, CM
镁离子，Mg 2+，是无数的生物化学过程所必需的，并且仍然是唯一的主要生物离子，其运输机制仍然未知。CorA家族的镁转运蛋白是大多数原核生物的主要Mg 2+摄取系统（1-3），也是真核线粒体镁转运蛋白的功能同源物（4）。在这里，我们确定晶体结构的全长Thermotoga maritima CorA在一个明显的封闭状态和其孤立的细胞质结构域在3.9埃和1.85埃的分辨率，分别。转运蛋白是一个漏斗状的同源五聚体，每个单体有两个跨膜螺旋。该通道由五个螺旋的内部组形成，并由大体积的疏水残基puprigated。大的胞质结构域形成一个漏斗，其宽口指向细胞内，其壁由五个长螺旋形成，这些长螺旋是跨膜螺旋的延伸。在漏斗的外侧，孔的细胞质颈被高度保守的带正电荷残基的环包围。细胞质结构域中的两个带负电荷的螺旋在漏斗的外侧向膜延伸并邻接正电荷环。一个明显的Mg 2+离子在细胞质结构域中的一个保守位点的单体之间的绑定，这表明一种机制，连接门控孔的细胞内浓度的Mg 2+。
The magnesium ion, Mg2+, is essential for myriad biochemical processes and remains the only major biological ion whose transport mechanisms remain unknown. The CorA family of magnesium transporters is the primary Mg2+ uptake system of most prokaryotes(1-3) and a functional homologue of the eukaryotic mitochondrial magnesium transporter(4). Here we determine crystal structures of the full-length Thermotoga maritima CorA in an apparent closed state and its isolated cytoplasmic domain at 3.9 angstrom and 1.85 angstrom resolution, respectively. The transporter is a funnel-shaped homopentamer with two transmembrane helices per monomer. The channel is formed by an inner group of five helices and putatively gated by bulky hydrophobic residues. The large cytoplasmic domain forms a funnel whose wide mouth points into the cell and whose walls are formed by five long helices that are extensions of the transmembrane helices. The cytoplasmic neck of the pore is surrounded, on the outside of the funnel, by a ring of highly conserved positively charged residues. Two negatively charged helices in the cytoplasmic domain extend back towards the membrane on the outside of the funnel and abut the ring of positive charge. An apparent Mg2+ ion was bound between monomers at a conserved site in the cytoplasmic domain, suggesting a mechanism to link gating of the pore to the intracellular concentration of Mg2+.