Three-dimensional solution structure of α-conotoxin MII by NMR spectroscopy:: Effects of solution environment on helicity
Three-dimensional solution structure of α-conotoxin MII by NMR spectroscopy:: Effects of solution environment on helicity
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DOI：
10.1021/bi981535w
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发表时间：
1998-11-10
期刊：
影响因子：
2.9
通讯作者：
Craik, DJ
中科院分区：
文献类型：
--
作者：
Hill, JM;Oomen, CJ;Craik, DJ
α-芋螺毒素MII是一种来自食鱼锥形蜗牛（Conusmagus）毒液的16个残基的多肽，是由α 3 β 2亚基组成的哺乳动物神经元烟碱乙酰胆碱受体的有效和高度特异性的阻断剂。这种受体类型在调节神经递质释放中的作用及其与成瘾和精神病问题的相关性强调了对MII与α 3 β 2界面相互作用模式的结构理解的重要性。在这里，我们描述的三维解决方案的结构MIT确定使用2D H-1 NMR光谱。结构约束包括376个质子间距离推断NOE和12个二面角的限制来自自旋-自旋耦合常数被用作模拟退火计算和能量最小化的程序X-PLOR输入。最后一组20个结构是非常明确的，在整个分子上，骨架原子的平均成对rms差为0.07埃，所有重原子的平均成对rms差为0.34埃。MII采用紧凑的结构，在N-和C-末端包含α-螺旋和β-转角的中心片段。该分子通过两个二硫键稳定，这两个二硫键在结构的N-末端与中间和C-末端之间提供交联。使用几种不同的溶剂条件下的结构，构象变化的敏感性进行了检查。虽然MII的整体折叠保持不变，但在通过向水溶液中加入乙腈或三氟乙醇提供的更疏水的环境中，结构得到稳定。氨基酸侧链在MII中的分布在其表面上产生不同的疏水性和极性斑块，这对于与α 3 β 2神经元nAChR的特异性相互作用可能是重要的。MII与其他神经元特异性α-芋螺毒素的结构的比较提供了它们与这些受体相互作用的模式的见解。
alpha-Conotoxin MII, a 16-residue polypeptide from the venom of the piscivorous cone snail Conus magus, is a potent and highly specific blocker of mammalian neuronal nicotinic acetylcholine receptors composed of alpha 3 beta 2 subunits. The role of this receptor type in the modulation of neurotransmitter release and its relevance to the problems of addiction and psychosis emphasize the importance of a structural understanding of the mode of interaction of MII with the alpha 3 beta 2 interface. Here we describe the three-dimensional solution structure of MIT determined using 2D H-1 NMR spectroscopy. Structural restraints consisting of 376 interproton distances inferred from NOEs and 12 dihedral restraints derived from spin-spin coupling constants were used as input for simulated annealing calculations and energy minimization in the program X-PLOR. The final set of 20 structures is exceptionally well-defined with mean pairwise rms differences over the whole molecule of 0.07 Angstrom for the backbone atoms and 0.34 Angstrom for all heavy atoms. MII adopts a compact structure incorporating a central segment of alpha-helix and beta-turns at the N- and C-termini. The molecule is stabilized by two disulfide bonds, which provide cross-links between the N-terminus and both the middle and C-terminus of the structure. The susceptibility of the structure to conformational change was examined using several different solvent conditions. While the global fold of MII remains the same, the structure is stabilized in a more hydrophobic environment provided by the addition of acetonitrile or trifluoroethanol to the aqueous solution. The distribution of amino acid side chains in MII creates distinct hydrophobic and polar patches on its surface that may be important for the specific interaction with the alpha 3 beta 2 neuronal nAChR. A comparison of the structure of MII with other neuronal-specific alpha-conotoxins provides insights into their mode of interaction with these receptors.