Solution structure and alanine scan of a spider toxin that affects the activation of mammalian voltage-gated sodium channels
Solution structure and alanine scan of a spider toxin that affects the activation of mammalian voltage-gated sodium channels
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DOI：
10.1074/jbc.m605403200
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发表时间：
2007-02-16
影响因子：
4.8
通讯作者：
Norton, Raymond S.
中科院分区：
文献类型：
--
作者：
Corzo, Gerardo;Sabo, Jennifer K.;Norton, Raymond S.
MAGI 5来自六足类蜘蛛Macrothele gias，是一种含有三个二硫键的29个残基的多肽。它特异性地结合到哺乳动物电压门控钠通道上的受体第4位，并与蝎子β毒素竞争，例如来自沼泽中心的CSSIV。因此，MAGI 5将哺乳动物rNav1.2a通道的激活电压转移到更超极化的电压，而昆虫通道DmNav1不受影响。为了深入了解毒素与通道的相互作用，合成了MAGI5和23个类似物。测定了MAGi5在水溶液中的三维结构，并利用一系列AlA取代类似物的电生理测量数据将其电压门控钠通道结合表面映射到该结构上。该结构明显类似于抑制物胱氨酸结结构基序，尽管在MAGI 5中典型的三链β-折叠被部分扭曲。MAGI 5朝向电压门控钠通道的相互作用表面在某些方面类似于Janus面的阿特拉科毒素，在毒素的一面有重要的带电残基，而在另一面有疏水残基。MAGI 5还类似于蝎子β毒素CSSIV，它有不同的非极性和带电表面，这是通道结合的关键，并且有一个关键的谷氨酸参与电压传感器捕获。这两类不同的毒素具有不同的氨基酸序列和不同的结构，它们可能利用其表面相似的残基来实现修饰电压门控钠通道功能的共同目的。
Magi 5, from the hexathelid spider Macrothele gigas, is a 29-residue polypeptide containing three disulfide bridges. It binds specifically to receptor site 4 on mammalian voltage-gated sodium channels and competes with scorpion beta-toxins, such as Css IV from Centruroides suffusus suffusus. As a consequence, Magi 5 shifts the activation voltage of the mammalian rNav1.2a channel to more hyperpolarized voltages, whereas the insect channel, DmNav1, is not affected. To gain insight into toxin-channel interactions, Magi 5 and 23 analogues were synthesized. The three-dimensional structure of Magi 5 in aqueous solution was determined, and its voltage-gated sodium channel-binding surfaces were mapped onto this structure using data from electrophysiological measurements on a series of Ala-substituted analogues. The structure clearly resembles the inhibitor cystine knot structural motif, although the triple-stranded beta-sheet typically found in that motif is partially distorted in Magi 5. The interactive surface of Magi 5 toward voltage-gated sodium channels resembles in some respects the Janus-faced atracotoxins, with functionally important charged residues on one face of the toxin and hydrophobic residues on the other. Magi 5 also resembles the scorpion beta-toxin Css IV, which has distinct nonpolar and charged surfaces that are critical for channel binding and has a key Glu involved in voltage sensor trapping. These two distinct classes of toxin, with different amino acid sequences and different structures, may utilize similar groups of residues on their surface to achieve the common end of modifying voltage-gated sodium channel function.