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首页> 外文期刊>Biochemistry >Differential agonist-induced displacement of quinacrine and ethidium from their respective histrionicotoxin-sensitive binding sites on the Torpedo acetylcholine receptor.
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Differential agonist-induced displacement of quinacrine and ethidium from their respective histrionicotoxin-sensitive binding sites on the Torpedo acetylcholine receptor.

机译：从鱼雷乙酰胆碱受体上它们各自的组织毒素敏感结合位点起差异性激动剂诱导的喹喔啉和乙胺置换。

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摘要

Fluorescence spectroscopy was used to begin to localize the agonist inhibitory binding site on the nicotinic acetylcholine receptor (AcChR) from Torpedo californica. High concentrations of three cholinergic agonists, suberyldicholine (SubCh), acetylcholine (AcCh), and carbamylcholine (CCh), differentially inhibited the binding of two noncompetitive inhibitors (NCIs), quinacrine and ethidium, which bind at distinctly different loci on the desensitized AcChR at zero membrane potential. The agonist-induced inhibition of quinacrine binding occurred at significantly lower (17-fold) concentrations than the inhibition of ethidium binding. Schild plots of SubCh inhibition of ethidium and quinacrine binding showed the competitive nature of the agonist inhibition of the binding of these two NCIs. The quenching constants for short-range quenching of receptor-bound quinacrine and ethidium fluorescence by spin-labeled acetylcholine were about the same as their inhibition constants for agonist-induced displacement of AcChR-bound quinacrine and ethidium. The results demonstrate that agonists can directly bind to both the quinacrine and the ethidium binding sites, albeit at different agonist concentrations. Because the agonist-induced displacement of receptor-bound quinacrine occurs at significantly lower concentrations than the displacement of ethidium, the quinacrine binding site is more likely than the ethidium binding site to form part of the agonist inhibitory binding site.
机译：荧光光谱法被用来开始定位来自加利福尼亚鱼雷的烟碱乙酰胆碱受体（AcChR）上的激动剂抑制性结合位点。高浓度的三种胆碱能激动剂，亚苄基胆碱（SubCh），乙酰胆碱（AcCh）和氨甲酰胆碱（CCh），差异性地抑制了两种非竞争性抑制剂（NCI）奎纳克林和乙啶的结合，这两种药物在脱敏的AcChR的不同基因座上结合零膜电位。激动剂引起的奎纳克林结合抑制作用的发生率比乙锭结合的抑制作用低得多（17倍）。 SubCh抑制乙锭和奎纳克林结合的Schild图显示了激动剂抑制这两种NCI结合的竞争性质。自旋标记的乙酰胆碱对受体结合的奎纳克林和乙锭荧光的短程猝灭的猝灭常数与激动剂诱导的AcChR结合的奎那克林和乙锭的置换的抑制常数大致相同。结果表明，即使激动剂浓度不同，激动剂也可以直接与奎纳克林和乙锭结合位点结合。因为激动剂诱导的受体结合喹啉的置换发生在比乙炔置换的浓度低得多的浓度下，所以喹ac碱结合部位比乙啶结合部位更可能形成激动剂抑制结合部位的一部分。

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