Loret E P, Martin-Eauclaire M F, Mansuelle P, Sampieri F, Granier C, Rochat H
Laboratoire de Biochimie, CNRS URA 1179, Faculté de Médecine, Secteur Nord, Marseille, France.
Biochemistry. 1991 Jan 22;30(3):633-40. doi: 10.1021/bi00217a007.
A new anti-insect neurotoxin, AaH IT4, has been isolated from the venom of the North African scorpion Androctonus australis Hector. This polypeptide has a toxic effect on insects and mammals and is capable of competing with anti-insect scorpion toxins for binding to the sodium channel of insects; it also modulates the binding of alpha-type and beta-type anti-mammal scorpion toxins to the mammal sodium channel. This is the first report of a scorpion toxin able to exhibit these three kinds of activity. The molecule is composed of 65 amino acid residues and lacks methionine and, more unexpectedly, proline, which until now has been considered to play a role in the folded structure of all scorpion neurotoxins. The primary structure showed a poor homology with the sequences of other scorpion toxins; however, it had features in common with beta-type toxins. In fact, radioimmunoassays using antibodies directed to scorpion toxins representative of the main structural groups showed that there is a recognition of AaH IT4 via anti-beta-type toxin antibodies only. A circular dichroism study revealed a low content of regular secondary structures, particularly in beta-sheet structures, when compared to other scorpion toxins. This protein might be the first member of a new class of toxins to have ancestral structural features and a wide toxic range.
一种新的抗昆虫神经毒素AaH IT4已从北非蝎子澳链尾蝎（Androctonus australis Hector）的毒液中分离出来。这种多肽对昆虫和哺乳动物都有毒性作用，并且能够与抗昆虫蝎子毒素竞争结合昆虫的钠通道；它还能调节α型和β型抗哺乳动物蝎子毒素与哺乳动物钠通道的结合。这是关于一种能够展现这三种活性的蝎子毒素的首次报道。该分子由65个氨基酸残基组成，缺少甲硫氨酸，更出人意料的是缺少脯氨酸，而脯氨酸直到现在都被认为在所有蝎子神经毒素的折叠结构中发挥作用。其一级结构与其他蝎子毒素的序列同源性较差；然而，它与β型毒素有共同特征。事实上，使用针对主要结构组代表性蝎子毒素的抗体进行的放射免疫分析表明，只有通过抗β型毒素抗体才能识别AaH IT4。圆二色性研究表明，与其他蝎子毒素相比，该蛋白的规则二级结构含量较低，尤其是β折叠结构。这种蛋白质可能是具有祖先结构特征和广泛毒性范围的新型毒素的首个成员。
