Electrostatic and steric contributions to block of the skeletal muscle sodium channel by mu-conotoxin.
Electrostatic and steric contributions to block of the skeletal muscle sodium channel by mu-conotoxin.
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DOI：
10.1085/jgp.119.1.45
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发表时间：
2002-01
期刊：
影响因子：
--
通讯作者：
French RJ
中科院分区：
文献类型：
--
作者：
Hui K;Lipkind G;Fozzard HA;French RJ
孔道阻断毒素是构成电信号基础的离子通道的有价值的探针。要成为有效的抑制剂，它们必须表现出高亲和力和特异性，并阻止离子传导。由22个残基组成的海螺肽μ-conotoxxGIIIA能完全阻断骨骼肌钠离子通道。部分封闭肽是通过对μ-芋螺毒素GIIIA中的单个或成对氨基酸进行替换而获得的，它允许对封堵机制进行新的分析。替换一个关键残基(Arg-13)产生的多肽仅部分阻断单通道电流。这些衍生物，以及其他同时取代第二个残基的衍生物，被用来阐明毒素封闭作用的结构基础。残基-13处的电荷是最引人注目的决定因素。对于完全阻断，正电荷是必要的，但不是充分的。封闭效率随着残基-13侧链大小的增加而增加，与电荷无关，这表明空间位阻对抑制作用有贡献。位于毒素分子一侧2、12和14位的电荷的影响较小，而位于毒素相反面的残基-16的影响较大。最直接的解释是，数据表明毒素的一侧通过与毛孔上的结合表面紧密结合而被掩盖，而另一侧含有Lys-16，暴露在一个可进入离子的水腔中。这种毒素表面产生了强烈的电荷依赖效应。在天然毒素中，Arg-13可能是一种战略性的静电屏障，而不是完全立体地封闭毛孔。这不同于其他众所周知的通道抑制剂，如钾通道阻滞剂的轮藻毒素家族和钠通道阻滞剂鸟粪毒素(河豚毒素和岩藻毒素)，后者似乎堵塞了狭窄的毛孔部分。
Pore-blocking toxins are valuable probes of ion channels that underlie electrical signaling. To be effective inhibitors, they must show high affinity and specificity and prevent ion conduction. The 22-residue sea snail peptide, μ-conotoxin GIIIA, blocks the skeletal muscle sodium channel completely. Partially blocking peptides, derived by making single or paired amino acid substitutions in μ-conotoxin GIIIA, allow a novel analysis of blocking mechanisms. Replacement of one critical residue (Arg-13) yielded peptides that only partially blocked single-channel current. These derivatives, and others with simultaneous substitution of a second residue, were used to elucidate the structural basis of the toxin's blocking action. The charge at residue-13 was the most striking determinant. A positive charge was necessary, though not sufficient, for complete block. Blocking efficacy increased with increasing residue-13 side chain size, regardless of charge, suggesting a steric contribution to inhibition. Charges grouped on one side of the toxin molecule at positions 2, 12, and 14 had a weaker influence, whereas residue-16, on the opposite face of the toxin, was more influential. Most directly interpreted, the data suggest that one side of the toxin is masked by close apposition to a binding surface on the pore, whereas the other side, bearing Lys-16, is exposed to an aqueous cavity accessible to entering ions. Strong charge-dependent effects emanate from this toxin surface. In the native toxin, Arg-13 probably presents a strategically placed electrostatic barrier rather than effecting a complete steric occlusion of the pore. This differs from other well-described channel inhibitors such as the charybdotoxin family of potassium channel blockers and the sodium channel-blocking guanidinium toxins (tetrodotoxin and saxitoxin), which appear to occlude the narrow part of the pore.
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影响因子：
56.9
作者：
Doyle, DA;Cabral, JM;MacKinnon, R
通讯作者：
MacKinnon, R
影响因子：
2.9
作者：
BECKER, S;PRUSAKSOCHACZEWSKI, E;FRENCH, RJ
通讯作者：
FRENCH, RJ
影响因子：
5.6
作者：
ANTOSIEWICZ, J;MCCAMMON, JA;GILSON, MK
通讯作者：
GILSON, MK
影响因子：
3.4
作者：
LIPKIND, GM;FOZZARD, HA
通讯作者：
FOZZARD, HA
影响因子：
16.2
作者：
French, RJ;PrusakSochaczewski, E;Horn, R
通讯作者：
Horn, R