STRUCTURAL CONSERVATION OF ION CONDUCTION PATHWAYS IN K-CHANNELS AND GLUTAMATE RECEPTORS
STRUCTURAL CONSERVATION OF ION CONDUCTION PATHWAYS IN K-CHANNELS AND GLUTAMATE RECEPTORS
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DOI：
10.1073/pnas.92.11.4882
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发表时间：
1995-05-23
影响因子：
11.1
通讯作者：
VANDONGEN, AMJ
中科院分区：
文献类型：
--
作者：
WOOD, MW;VANDONGEN, HMA;VANDONGEN, AMJ
单通道记录表明，离子通道在开放和关闭的孔道构象之间随机切换，为了寻找这种普遍的开放/关闭行为的结构解释，我们发现电压门控K通道和谷氨酸受体的成孔区之间存在惊人的氨基酸同源性，这表明这些原本不相关的通道的孔可能在结构上是保守的。强有力的实验证据支持K通道成孔区的发夹结构，因此，我们假设谷氨酸受体的孔存在类似的结构，在配体门控通道中，孔是由四个假定的跨膜片段中的第二个M2形成的，M2的发夹结构将影响随后的膜拓扑，颠倒下一个片段M3的方向，我们已经对N-甲基-D-天冬氨酸受体的NR1亚单位的这一想法进行了检验。影响NR1亚单位糖基化模式的突变使M3-M4连接子的两端都定位于细胞外空间，全细胞电流和表观激动剂亲和力不受这些突变的影响，因此可以假设它们代表了天然的跨膜拓扑，M3-M4连接子的细胞外分配通过倒置M3来挑战当前的拓扑模型，综上所述，氨基酸同源性和新的拓扑结构表明，谷氨酸受体的造孔M2片段不会横跨膜，而是形成一个发夹结构，类似于在K通道中发现的结构。
Single channel recordings demonstrate that ion channels switch stochastically between an open and a closed pore conformation, In search of a structural explanation for this universal open/close behavior, we have uncovered a striking degree of amino acid homology across the pore-forming regions of voltage-gated K channels and glutamate receptors, This suggested that the pores of these otherwise unrelated classes of channels could be structurally conserved. Strong experimental evidence supports a hairpin structure for the pore-forming region of K channels, Consequently, we hypothesized the existence of a similar structure for the pore of glutamate receptors, In ligand-gated channels, the pore is formed by M2, the second of four putative transmembrane segments, A hairpin structure for M2 would affect the subsequent membrane topology, inverting the proposed orientation of the next segment, M3, We have tested this idea for the NR1 subunit of the N-methyl-D-aspartate receptor. Mutations that affected the glycosylation pattern of the NR1 subunit localize both extremes of the M3-M4 linker to the extracellular space, Whole cell currents and apparent agonist affinities were not affected by these mutations, Therefore it can be assumed that they represent the native transmembrane topology, The extracellular assignment of the M3-M4 linker challenged the current topology model by inverting M3, Taken together, the amino acid homology and the new topology suggest that the pore-forming M2 segment of glutamate receptors does not transverse the membrane but, rather, forms a hairpin structure, similar to that found in K channels.