Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China.
Toxicon. 2013 Mar 1;63:129-36. doi: 10.1016/j.toxicon.2012.12.001. Epub 2012 Dec 13.
With high binding affinity and distinct pharmacological functions, animal toxins are powerful ligands to investigate the structure-function relationships of voltage-gated ion channels. Jingzhaotoxin-I (JZTX-I) is an important neurotoxin from the tarantula Chilobrachys jingzhao venom that inhibits both sodium and potassium channels. In our previous work, JZTX-I, as a gating modifier, is able to inhibit activation of the potassium channel subtype Kv2.1. However, its binding site on Kv2.1 remains unknown. In this study, using Ala-scanning mutagenesis strategy, we demonstrated that four residues (I273, F274, E277, and K280) in S3b-S4 motif contributed to the formation of JZTX-I binding site. The mutations I273A, F274A, E277A, and K280A reduced toxin binding affinity by 6-, 10-, 8-, and 7-fold, respectively. Taken together with our previous data that JZTX-I accelerated channel deactivation, these results suggest that JZTX-I inhibits Kv2.1 activation by docking onto the voltage sensor paddle and trapping the voltage sensor in the closed state.
具有高结合亲和力和独特药理学功能的动物毒素是研究电压门控离子通道结构-功能关系的强大配体。 Jingzhaotoxin-I (JZTX-I) 是来自蜘蛛 Chilobrachys jingzhao 毒液的一种重要神经毒素，它能抑制钠和钾通道。在我们之前的工作中，JZTX-I 作为一种门控修饰剂，能够抑制钾通道亚型 Kv2.1 的激活。然而，其在 Kv2.1 上的结合位点仍不清楚。在这项研究中，我们使用 Ala 扫描突变策略，证明 S3b-S4 基序中的四个残基 (I273、F274、E277 和 K280) 有助于形成 JZTX-I 的结合位点。突变 I273A、F274A、E277A 和 K280A 使毒素结合亲和力分别降低了 6 倍、10 倍、8 倍和 7 倍。结合我们之前的数据，即 JZTX-I 加速通道失活，这些结果表明 JZTX-I 通过对接电压传感器桨叶并将电压传感器固定在关闭状态来抑制 Kv2.1 的激活。
