RINGS OF NEGATIVELY CHARGED AMINO-ACIDS DETERMINE THE ACETYLCHOLINE-RECEPTOR CHANNEL CONDUCTANCE
RINGS OF NEGATIVELY CHARGED AMINO-ACIDS DETERMINE THE ACETYLCHOLINE-RECEPTOR CHANNEL CONDUCTANCE
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DOI：
10.1038/335645a0
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发表时间：
1988-10-13
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;BUSCH, C;NUMA, S
利用互补DNA操作和单通道电流分析相结合的方法有效地研究了烟碱乙酰胆碱受体（AChR）的结构-功能关系1 - 6。先前对加利福尼亚鱼雷和牛AChR δ亚基的嵌合体的研究表明，由疏水段M2及其附近组成的区域包含了离子通过AChR通道传输速率的重要决定因素5。也有人认为，该区域负责二价阳离子引起的通道电导降低5，而M2段有助于非竞争性拮抗剂的结合位点7,8。为了识别那些与渗透离子相互作用的氨基酸残基，我们在鱼雷achr亚基cdna中引入了各种点突变，以改变跨膜片段周围带电或谷氨酰胺残基的净电荷[9 - 15]。这些AChR突变体在非洲爪猴卵母细胞中表达的单通道电导特性表明，在α-、β-、γ-和δ-亚基的M2段附近，可能形成三个阴离子环，三簇带负电荷和谷氨酰胺残基是离子运输速率的主要决定因素。
The structure–function relationship of the nicotinic acetylcholine receptor (AChR) has been effectively studied by the combination of complementary DNA manipulation and single-channel current analysis1–6. Previous work with chimaeras between theTorpedo californicaand bovine AChR δ-subunits has shown that the region comprising the hydrophobic segment M2 and its vicinity contains an important determinant of the rate of ion transport through the AChR channel5. It has also been suggested that this region is responsible for the reduction in channel conductance caused by divalent cations5and that segment M2 contributes to the binding site of noncompetitive antagonists7,8. To identify those amino acid residues that interact with permeating ions, we have introduced various point mutations into theTorpedoAChR subunit cDNAs to alter the net charge of the charged or glutamine residues around the proposed transmembrane segments9–15. The single-channel conductance properties of these AChR mutants expressed inXenopus laevisoocytes indicate that three clusters of negatively charged and glutamine residues neighbouring segment M2 of the α-, β-, γ- and δ-subunits, probably forming three anionic rings, are major determinants of the rate of ion transport.