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首页> 外文期刊>Canadian Journal of Physiology and Pharmacology >Properties of specific binding site of myotoxin a, a powerful convulsant, in brain microsomes.
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Properties of specific binding site of myotoxin a, a powerful convulsant, in brain microsomes.

机译：脑微粒体中强大的惊厥药肌毒素a的特异性结合位点的特性。

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摘要

Myotoxin a, a small basic polypeptide from prairie rattlesnakes (Crotalus viridis viridis), induces myonecrosis and binds to a single class of binding sites in skeletal muscle sarcoplasmic reticulum. In the present study, [125I]myotoxin a with a high specific activity was prepared and it was shown to bind mainly to microsomes in rat whole brain. [125I]Myotoxin a was further shown to bind to microsomes prepared from all regions tested in brain. Its specific binding to whole brain microsomes was of approximately 1.9 times lower affinity (KD = 0.76 microM; Bmax = 13.1 nmol/mg) than that to skeletal muscle sarcoplasmic reticulum. [125I]Myotoxin a binding to brain microsomes was displaced by unlabeled myotoxin a with an IC50 value of 4.5 microM. [125I]Myotoxin a binding was markedly reduced by treatment of microsomes with trypsin, suggesting that the binding site of [125I]myotoxin a is partially proteins. The binding was significantly inhibited by Mg2+ at concentrations above 1 mM. Having looked at several drugs, we noted that [125I]myotoxin a binding was noncompetitively inhibited by spermine, whereas it was enhanced by heparin. On the other hand, the i.c.v. injection of myotoxin a in mice induced potent convulsive effects at 0.05 nmol/mouse or more. This paper is the first to show that the specific binding site of myotoxin a is present in mouse brain and that myotoxin a is a novel peptidic convulsant in mice.
机译：肌毒素a是草原响尾蛇（Crotalus viridis viridis）的一种很小的基本多肽，可诱导肌坏死并与骨骼肌肌浆网中的一类结合位点结合。在本研究中，制备了具有高比活性的[125I]肌毒素a，并显示它主要与大鼠全脑中的微粒体结合。进一步显示[125I]肌毒素a与从脑中测试的所有区域制备的微粒体结合。它与全脑微粒体的特异性结合比对骨骼肌肌浆网的特异性结合低约1.9倍（KD = 0.76 microM; Bmax = 13.1 nmol / mg）。 [125I]与脑微粒体结合的肌毒素a被未标记的肌毒素a取代，其IC50值为4.5 microM。通过用胰蛋白酶处理微粒体，[125I]肌毒素a的结合显着降低，表明[125I]肌毒素a的结合位点是部分蛋白质。在1 mM以上的浓度下，Mg2 +显着抑制了结合。查看了几种药物后，我们注意到精胺非竞争性地抑制[125I]肌毒素a的结合，而肝素则增强了这种结合。另一方面，i.c.v。在小鼠中注射肌毒素a会以0.05 nmol /小鼠或更高的剂量诱导强效惊厥作用。这篇论文是第一个表明小鼠脑中存在肌毒素a的特异性结合位点，并且肌毒素a是小鼠中一种新型的肽惊厥剂。

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