Ohkura M, Ide T, Furukawa K, Kawasaki T, Kasai M, Ohizumi Y
Department of Pharmaceutical Molecular Biology, Tohoku University, Sendai, Japan.
Can J Physiol Pharmacol. 1995 Aug;73(8):1181-5. doi: 10.1139/y95-167.
Myotoxin alpha (MYTX), a polypeptide toxin purified from the venom of prairie rattlesnakes (Crotalus viridis viridis), induced Ca2+ release from the heavy fraction of skeletal sarcoplasmic reticulum (HSR), using a Ca2+ electrode. The effect of MYTX was nearly abolished by pretreatment with ryanodine, an alkaloid-based Ca2+ channel blocker. In the stopped-flow experiments, MYTX increased the choline+ permeability of HSR in the presence of calsequestrin (CS). Single channel recording experiments showed that in the presence of CS, the channel currents were markedly enhanced by MYTX applied to the cis side, but not to the trans side. However, in the absence of CS, MYTX failed to cause the excitatory effect in both the experiments. These results suggest that CS is essential for MYTX-induced Ca2+ release through the Ca2+ release channels in skeletal HSR.
α-肌毒素（MYTX）是一种从草原响尾蛇（Crotalus viridis viridis）毒液中纯化得到的多肽毒素，利用钙离子电极，它可诱导从骨骼肌肌浆网重质组分（HSR）中释放钙离子。用基于生物碱的钙离子通道阻滞剂钌红预处理后，MYTX的作用几乎完全消失。在停流实验中，在存在肌集钙蛋白（CS）的情况下，MYTX增加了HSR对胆碱+的通透性。单通道记录实验表明，在存在CS的情况下，施加于顺式侧的MYTX可显著增强通道电流，但施加于反式侧则无此作用。然而，在不存在CS的情况下，在这两个实验中MYTX均未能产生兴奋作用。这些结果表明，CS对于MYTX通过骨骼肌HSR中的钙离子释放通道诱导钙离子释放至关重要。
