LOCATION OF A DELTA-SUBUNIT REGION DETERMINING ION-TRANSPORT THROUGH THE ACETYLCHOLINE-RECEPTOR CHANNEL
LOCATION OF A DELTA-SUBUNIT REGION DETERMINING ION-TRANSPORT THROUGH THE ACETYLCHOLINE-RECEPTOR CHANNEL
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DOI：
10.1038/324670a0
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发表时间：
1986-12-18
期刊：
影响因子：
64.8
通讯作者：
NUMA, S
中科院分区：
文献类型：
--
作者：
IMOTO, K;METHFESSEL, C;NUMA, S
互补DNA表达和单通道电流分析的结合为研究烟碱乙酰胆碱受体（AChR）的结构-功能关系提供了有力的工具（参考文献1-5）。我们以前已经表明，AChR通道由来自不同物种的亚基组成，表达在异种卵母细胞的表面膜中，可用于将功能特性与单个亚基联系起来4。本文报道了在二价阳离子浓度较低的细胞外溶液中，牛AChR通道的电导比电鳐AChR通道的电导小。将TorpedoAChR的δ-亚基替换为牛δ-亚基，使通道电导与牛AChR通道相似。为了定位δ亚基中导致这种差异的区域，我们构建了具有不同组合的电鳐和牛对应物的嵌合δ亚基cDNA。含有嵌合δ亚基的AChR通道的电导表明，包含推定的跨膜节段M2和节段M2和M3之间的相邻弯曲部分的区域参与决定通过开放通道的离子转运速率。
The combination of complementary DNA expression and single-channel current analysis provides a powerful tool for studying the structure–function relationship of the nicotinic acetylcholine receptor (AChR) (refs 1–5). We have previously shown that AChR channels consisting of subunits from different species, expressed in the surface membrane ofXenopusoocytes, can be used to relate functional properties to individual subunits4. Here we report that, in extracellular solution of low divalent cation concentration, the bovine AChR channel has a smaller conductance than theTorpedoAChR channel. Replacement of theδ-subunit of theTorpedoAChR by the bovineδ-subunit makes the channel conductance similar to that of the bovine AChR channel. To locate the region in theδ-subunit responsible for this difference, we have constructed chimaericδ-subunit cDNAs with different combinations of theTorpedoand bovine counterparts. The conductances of AChR channels containing chimaericδ-subunits suggest that a region comprising the putative transmembrane segment M2 and the adjacent bend portion between segments M2 and M3 is involved in determining the rate of ion transport through the open channel.