Scorpion Potassium Channel-blocking Defensin Highlights a Functional Link with Neurotoxin
Scorpion Potassium Channel-blocking Defensin Highlights a Functional Link with Neurotoxin
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蝎子钾通道阻断防御素凸显了与神经毒素的功能联系
DOI：
10.1074/jbc.m115.680611
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发表时间：
2016-03-25
影响因子：
4.8
通讯作者：
Wu, Yingliang
中科院分区：
文献类型：
--
作者：
Meng, Lanxia;Xie, Zili;Wu, Yingliang
防御素和蝎子神经毒素之间的结构相似性表明它们可能是从一个共同的祖先进化而来的。然而，没有直接的实验证据表明蝎子神经毒素和防御素之间的功能联系。蝎防御素BmKDfsin 4由37个氨基酸残基和一个保守的胱氨酸稳定/结构折叠组成。重组BmKDfsin 4是一种经典的防御素，已被发现对革兰氏阳性菌如金黄色葡萄球菌、枯草芽孢杆菌和藤黄微球菌以及耐甲氧西林金黄色葡萄球菌具有抑制活性。有趣的是，电生理实验表明，BmKDfsin 4像蝎子钾通道神经毒素一样，可以有效地抑制Kv1.1，Kv1.2和Kv1.3通道电流，其对Kv1.3通道的IC 50值为510.2 nm。与经典的蝎钾通道阻断毒素的结构-功能关系相似，BmKDfsin 4的碱性残基（Lys-13和Arg-19）在肽-Kv 1.3通道相互作用中起关键作用。此外，突变和电生理实验证明BmKDfsin 4的结合位点位于通道细胞外孔区，表明BmKDfsin 4具有与经典蝎毒素相同的钾通道阻断机制。总之，我们的工作确定蝎子BmKDfsin 4作为第一个无脊椎动物防御素阻断钾通道。这些发现不仅证明了无脊椎动物防御素是一种新型的钾离子通道阻断剂，而且为防御素和神经毒素之间的功能联系提供了证据。
The structural similarity between defensins and scorpion neurotoxins suggests that they might have evolved from a common ancestor. However, there is no direct experimental evidence demonstrating a functional link between scorpion neurotoxins and defensins. The scorpion defensin BmKDfsin4 from Mesobuthus martensii Karsch contains 37 amino acid residues and a conserved cystine-stabilized / structural fold. The recombinant BmKDfsin4, a classical defensin, has been found to have inhibitory activity against Gram-positive bacteria such as Staphylococcus aureus, Bacillus subtilis, and Micrococcus luteus as well as methicillin-resistant Staphylococcus aureus. Interestingly, electrophysiological experiments showed that BmKDfsin4,like scorpion potassium channel neurotoxins, could effectively inhibit Kv1.1, Kv1.2, and Kv1.3 channel currents, and its IC50 value for the Kv1.3 channel was 510.2 nm. Similar to the structure-function relationships of classical scorpion potassium channel-blocking toxins, basic residues (Lys-13 and Arg-19) of BmKDfsin4 play critical roles in peptide-Kv1.3 channel interactions. Furthermore, mutagenesis and electrophysiological experiments demonstrated that the channel extracellular pore region is the binding site of BmKDfsin4, indicating that BmKDfsin4adopts the same mechanism for blocking potassium channel currents as classical scorpion toxins. Taken together, our work identifies scorpion BmKDfsin4 as the first invertebrate defensin to block potassium channels. These findings not only demonstrate that defensins from invertebrate animals are a novel type of potassium channel blockers but also provide evidence of a functional link between defensins and neurotoxins.