Pallaghy P K, Duggan B M, Pennington M W, Norton R S
NMR Laboratory, Biomolecular Research Institute, Parkville, Australia.
J Mol Biol. 1993 Nov 20;234(2):405-20. doi: 10.1006/jmbi.1993.1595.
The 27 amino acid residue polypeptide omega-conotoxin GVIA, from venom of the cone shell Conus geographus, blocks neuronal voltage-activated calcium channels at picomolar concentrations. The three-dimensional structure in aqueous solution of synthetic omega-conotoxin has been determined from two-dimensional 1H n.m.r. data recorded at 600 MHz. Structural constraints consisting of interproton distances inferred from NOEs and dihedral angles from spin-spin coupling constants were used as input for distance geometry calculations with the program DSPACE. The structures were then refined using back-calculation of NOESY spectra. The family of structures obtained in this way is well defined by the n.m.r. data, the best 12 structures having pairwise root-mean-square differences of 0.68 (+/- 0.15) A over the backbone heavy atoms (N, C alpha and C) and 1.15 (+/- 0.17) A over all heavy-atoms. The molecule adopts a compact structure consisting of a small, triple-stranded, anti-parallel beta-sheet and several reverse turns. All three tyrosine residues are located on the molecular surface, which is noteworthy for its abundance of side-chain hydroxyl groups. There is no negatively charged group in conotoxin, but the five positively charged groups are distributed in three small patches on the surface, one of which, made up of the ammonium moieties of the N terminus and Lys2, may contribute to the receptor-binding surface of the molecule. An isomer of conotoxin with the same amino acid sequence, but different disulfide pairings, has also been investigated. Its structure is less well ordered than that of native conotoxin and it shows significant heterogeneity, probably as a result of cis-trans isomerism preceding hydroxyproline residues.
来自地纹芋螺毒液的由27个氨基酸残基组成的多肽ω-芋螺毒素GVIA，在皮摩尔浓度下就能阻断神经元电压激活的钙通道。已根据在600 MHz下记录的二维¹H核磁共振数据确定了合成ω-芋螺毒素在水溶液中的三维结构。由从核Overhauser效应（NOE）推断出的质子间距离和自旋-自旋耦合常数得出的二面角组成的结构约束条件，被用作使用DSPACE程序进行距离几何计算的输入。然后通过NOESY谱的反计算对结构进行优化。通过这种方式获得的结构家族由核磁共振数据很好地定义，最佳的12个结构在主链重原子（N、Cα和C）上的成对均方根偏差为0.68（±0.15）Å，在所有重原子上为1.15（±0.17）Å。该分子采用紧凑结构，由一个小的三股反平行β-折叠和几个反向转角组成。所有三个酪氨酸残基都位于分子表面，其侧链羟基丰富，这一点值得注意。芋螺毒素中没有带负电荷的基团，但五个带正电荷的基团分布在表面的三个小区域中，其中一个由N端的铵基和Lys2组成，可能有助于分子的受体结合表面。还研究了一种具有相同氨基酸序列但二硫键配对不同的芋螺毒素异构体。其结构的有序性不如天然芋螺毒素，并且显示出明显的异质性，这可能是由于羟脯氨酸残基之前的顺反异构现象导致的。
