Lange Adam, Giller Karin, Hornig Sönke, Martin-Eauclaire Marie-France, Pongs Olaf, Becker Stefan, Baldus Marc
Max Planck Institute for Biophysical Chemistry, Department of NMR-Based Structural Biology, 37077 Göttingen, Germany.
Nature. 2006 Apr 13;440(7086):959-62. doi: 10.1038/nature04649.
The active site of potassium (K+) channels catalyses the transport of K+ ions across the plasma membrane--similar to the catalytic function of the active site of an enzyme--and is inhibited by toxins from scorpion venom. On the basis of the conserved structures of K+ pore regions and scorpion toxins, detailed structures for the K+ channel-scorpion toxin binding interface have been proposed. In these models and in previous solution-state nuclear magnetic resonance (NMR) studies using detergent-solubilized membrane proteins, scorpion toxins were docked to the extracellular entrance of the K+ channel pore assuming rigid, preformed binding sites. Using high-resolution solid-state NMR spectroscopy, here we show that high-affinity binding of the scorpion toxin kaliotoxin to a chimaeric K+ channel (KcsA-Kv1.3) is associated with significant structural rearrangements in both molecules. Our approach involves a combined analysis of chemical shifts and proton-proton distances and demonstrates that solid-state NMR is a sensitive method for analysing the structure of a membrane protein-inhibitor complex. We propose that structural flexibility of the K+ channel and the toxin represents an important determinant for the high specificity of toxin-K+ channel interactions.
钾离子（K+）通道的活性位点催化K+离子穿过质膜——类似于酶活性位点的催化功能——并受到蝎毒毒素的抑制。基于K+通道孔区域和蝎毒素的保守结构，人们提出了K+通道-蝎毒素结合界面的详细结构。在这些模型以及此前使用去污剂增溶膜蛋白进行的溶液态核磁共振（NMR）研究中，蝎毒素被对接至K+通道孔的细胞外入口，假定存在刚性的、预先形成的结合位点。利用高分辨率固态核磁共振光谱技术，我们在此表明蝎毒素卡利毒素与嵌合K+通道（KcsA-Kv1.3）的高亲和力结合与两个分子中的显著结构重排相关。我们的方法涉及化学位移和质子-质子距离的联合分析，并证明固态核磁共振是分析膜蛋白-抑制剂复合物结构的一种灵敏方法。我们提出，K+通道和毒素的结构灵活性代表了毒素-K+通道相互作用高特异性的一个重要决定因素。
