Department of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea.
Toxicology and Pharmacology, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N2, P.O. Box 922, Leuven 3000, Belgium.
BMB Rep. 2020 May;53(5):260-265. doi: 10.5483/BMBRep.2020.53.5.256.
Scorpion venom comprises a cocktail of toxins that have proven to be useful molecular tools for studying the pharmacological properties of membrane ion channels. HelaTx1, a short peptide neurotoxin isolated recently from the venom of the scorpion Heterometrus laoticus, is a 25 amino acid peptide with two disulfide bonds that shares low sequence homology with other scorpion toxins. HelaTx1 effectively decreases the amplitude of the K+ currents of voltage-gated Kv1.1 and Kv1.6 channels expressed in Xenopus oocytes, and was identified as the first toxin member of the κ-KTx5 subfamily, based on a sequence comparison and phylogenetic analysis. In the present study, we report the NMR solution structure of HelaTx1, and the major interaction points for its binding to voltage-gated Kv1.1 channels. The NMR results indicate that HelaTx1 adopts a helix-loop-helix fold linked by two disulfide bonds without any β-sheets, resembling the molecular folding of other cysteine-stabilized helix-loop-helix (Cs α/α) scorpion toxins such as κ-hefutoxin, HeTx, and OmTx, as well as conotoxin pl14a. A series of alanine-scanning analogs revealed a broad surface on the toxin molecule largely comprising positively-charged residues that is crucial for interaction with voltagegated Kv1.1 channels. Interestingly, the functional dyad, a key molecular determinant for activity against voltage-gated potassium channels in other toxins, is not present in HelaTx1. [BMB Reports 2020; 53(5): 260-265].
蝎毒液包含多种毒素，这些毒素已被证明是研究膜离子通道药理学特性的有用分子工具。最近从 Heterometrus laoticus 蝎毒液中分离得到的短肽神经毒素 HelaTx1 是一种 25 个氨基酸的肽，含有两个二硫键，与其他蝎毒素的序列同源性较低。HelaTx1 可有效降低电压门控 Kv1.1 和 Kv1.6 通道在非洲爪蟾卵母细胞中表达的 K+电流幅度，并基于序列比较和系统发育分析被鉴定为 κ-KTx5 亚家族的第一个毒素成员。在本研究中，我们报告了 HelaTx1 的 NMR 溶液结构，以及其与电压门控 Kv1.1 通道结合的主要相互作用点。NMR 结果表明，HelaTx1 采用由两个二硫键连接的螺旋-环-螺旋折叠，没有任何β-折叠，类似于其他半胱氨酸稳定的螺旋-环-螺旋（Cs α/α）蝎毒素（如 κ-hefutoxin、HeTx 和 OmTx）以及芋螺毒素 pl14a 的分子折叠。一系列丙氨酸扫描类似物揭示了毒素分子上的一个广泛的表面，主要由带正电荷的残基组成，这对于与电压门控 Kv1.1 通道相互作用至关重要。有趣的是，功能二联体，即其他毒素中针对电压门控钾通道活性的关键分子决定因素，在 HelaTx1 中不存在。[BMB Reports 2020; 53(5): 260-265]。
