NEGATIVELY CHARGED AMINO-ACID-RESIDUES IN THE NICOTINIC RECEPTOR DELTA-SUBUNIT THAT CONTRIBUTE TO THE BINDING OF ACETYLCHOLINE
NEGATIVELY CHARGED AMINO-ACID-RESIDUES IN THE NICOTINIC RECEPTOR DELTA-SUBUNIT THAT CONTRIBUTE TO THE BINDING OF ACETYLCHOLINE
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DOI：
10.1073/pnas.90.13.6285
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发表时间：
1993-07-01
影响因子：
11.1
通讯作者：
KARLIN, A
中科院分区：
文献类型：
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作者：
CZAJKOWSKI, C;KAUFMANN, C;KARLIN, A
在烟碱受体中，乙酰胆碱的结合位点可能包含带负电荷的氨基酸侧链，其与乙酰胆碱和其他有效激动剂的带正电荷的季铵基团相互作用。我们之前发现，δ 亚基的 61 个残基片段在 α 亚基上乙酰胆碱结合位点的半胱氨酸 1 nm 范围内含有天冬氨酸或谷氨酸残基。我们现在已经对小鼠肌肉δ亚基的这一片段中的12种天冬氨酸和谷氨酸进行了一次突变，并在非洲爪蟾卵母细胞中表达了突变受体。引起半最大电流（K(app)）的乙酰胆碱浓度和乙酰胆碱抑制α-金环蛇毒素结合的K(i)均因deltaAsp180突变为Asn而增加了100倍，因deltaGlu189突变为Gln而增加了10倍。这两个残基及其在γ和ε亚基中的同源物可能有助于乙酰胆碱结合位点。
In nicotinic receptors, the binding sites for acetylcholine are likely to contain negatively charged amino acid side chains that interact with the positively charged quaternary ammonium group of acetylcholine and of other potent agonists. We previously found that a 61-residue segment of the delta subunit contains aspartate or glutamate residues within 1 nm of cysteines in the acetylcholine binding site on the alpha subunit. We have now mutated, one at a time, the 12 aspartates and glutamates in this segment of the mouse muscle delta subunit and have expressed the mutant receptors in Xenopus oocytes. Both the concentration of acetylcholine eliciting half-maximal current (K(app)) and the K(i) for the inhibition by acetylcholine of alpha-bungarotoxin binding were increased 100-fold by the mutation of deltaAsp180 to Asn and 10-fold by the mutation of deltaGlu189 to Gln. These two residues, and their homologs in the gamma and epsilon subunits, are likely to contribute to the acetylcholine binding sites.