O'Leary M E, Krueger B K
Department of Physiology, University of Maryland School of Medicine, Baltimore 21201.
Mol Pharmacol. 1989 Nov;36(5):789-95.
The combined effects of batrachotoxin (BTX) and either scorpion (Leiurus quinquestriatus quinquestriatus) venom (LqqV) or alpha-scorpion toxin (alpha-LqqTX) purified from LqqV on single voltage-gated Na channels were studied in planar lipid bilayers. In the presence of BTX, LqqV caused the channels to remain open at membrane potentials at least 50 mV more hyperpolarized than with BTX alone. alpha-LqqTX mimicked the effect of LqqV, suggesting that this toxin is the active component of the venom. LqqV did not significantly alter single-channel conductance, voltage-dependent block by saxitoxin, or voltage-dependent block by Ca2+, indicating that the venom preferentially affects gating rather than ion permeation. The results indicate that a cooperative interaction between alpha-LqqTX and BTX strongly favors the open state of the Na channel by causing a large hyperpolarizing shift in the voltage dependence of activation. This effect on activation gating is not predicted from the individual effects of the toxins.
在平面脂质双分子层中研究了蛙毒素（BTX）与从以色列金蝎（Leiurus quinquestriatus quinquestriatus）毒液（LqqV）中纯化得到的蝎毒或α-蝎毒素（α-LqqTX）对单个电压门控钠通道的联合作用。在存在BTX的情况下，LqqV使通道在比单独使用BTX时至少超极化50 mV的膜电位下保持开放。α-LqqTX模拟了LqqV的作用，表明该毒素是毒液的活性成分。LqqV并未显著改变单通道电导、石房蛤毒素的电压依赖性阻断或Ca2+的电压依赖性阻断，表明该毒液优先影响门控而非离子通透。结果表明，α-LqqTX与BTX之间的协同相互作用通过使激活的电压依赖性发生大幅超极化偏移，强烈有利于钠通道的开放状态。这种对激活门控的作用无法从毒素的单独作用中预测出来。
