Complex between α-bungarotoxin and an α7 nicotinic receptor ligand-binding domain chimaera.
Complex between α-bungarotoxin and an α7 nicotinic receptor ligand-binding domain chimaera.
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DOI：
10.1042/bj20130636
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发表时间：
2013-09-01
期刊：
影响因子：
--
通讯作者：
Sine SM
中科院分区：
文献类型：
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作者：
Huang S;Li SX;Bren N;Cheng K;Gomoto R;Chen L;Sine SM
为了鉴定长链α-神经毒素与烟碱受体之间的高亲和力相互作用，我们确定了α-btx（α-银环蛇毒素）与由人α7 AChR（乙酰胆碱受体）和AChBP（乙酰胆碱结合蛋白）构建的五聚体配体结合结构域之间的复合物的晶体结构。该复合物的表面积约为2000 μ 2（1 μ = 0.1 nm），其中来自α-btx的指II的Arg 36和Phe 32形成π-阳离子堆叠，与来自α7的环C的保守Tyr 184边对面对齐，而α-btx的Asp 30与Tyr 184的羟基形成氢键。这些残基间相互作用不同于α-ctx（α-眼镜蛇毒素）与AChBP结合的4.2 π结构，但与α-btx与单体α1胞外结构域结合的1.94 π结构相似，尽管与单体结合的复合物相比，α-btx骨架相对于蛋白质表面表现出较大的位移。突变分析表明，用苏氨酸残基取代Tyr 184可消除高亲和力α-btx结合，而用苯丙氨酸残基取代可保持高亲和力。α-btx复合物与激动剂epibatidine偶联的复合物的比较揭示了结合口袋内和每个亚基中的结构重排。总体研究结果突出了α-神经毒素与烟碱受体相互作用的结构原理。
To identify high-affinity interactions between long-chain α-neurotoxins and nicotinic receptors, we determined the crystal structure of the complex between α-btx (α-bungarotoxin) and a pentameric ligand-binding domain constructed from the human α7 AChR (acetylcholine receptor) and AChBP (acetylcholine-binding protein). The complex buries ~2000 Å2 (1 Å = 0.1 nm) of surface area, within which Arg36 and Phe32 from finger II of α-btx form a π-cation stack that aligns edge-to-face with the conserved Tyr184 from loop-C of α7, while Asp30 of α-btx forms a hydrogen bond with the hydroxy group of Tyr184. These inter-residue interactions diverge from those in a 4.2 Å structure of α-ctx (α-cobratoxin) bound to AChBP, but are similar to those in a 1.94 Å structure of α-btx bound to the monomeric α1 extracellular domain, although compared with the monomer-bound complex, the α-btx backbone exhibits a large shift relative to the protein surface. Mutational analyses show that replacing Tyr184 with a threonine residue abolishes high-affinity α-btx binding, whereas replacing with a phenylalanine residue maintains high affinity. Comparison of the α-btx complex with that coupled to the agonist epibatidine reveals structural rearrangements within the binding pocket and throughout each subunit. The overall findings high-light structural principles by which α-neurotoxins interact with nicotinic receptors.