Martins J C, Van de Ven F J, Borremans F A
Vakgebied Biomoleculaire NMR, Vakgroep Organische Chemie, Universiteit Gent, Belgium.
J Mol Biol. 1995 Nov 3;253(4):590-603. doi: 10.1006/jmbi.1995.0575.
The three-dimensional solution structure of Scyllatoxin (leiurotoxin I) a venom peptide from the scorpion Leiurus quinquestriatus hebraeus was determined at 1 A resolution by homonuclear proton n.m.r. methods at 500 MHz. Data analysis and structure calculation followed conventional protocols inherent to DIANA and related programs with two exceptions. First, distance constraints were obtained from two-dimensional nuclear Overhauser spectra by a previously described partial relaxation matrix approach. Second, since the pairing pattern of the six cysteine residues was not established a priori, the unequivocal assignment of the disulfide bridges was achieved exclusively from the n.m.r. data by a statistical analysis of preliminary DIANA structures. In the final calculation we used 227 upper distance constraints, 67 torsional constraints from vicinal coupling constants and ten stereospecific assignments of beta-methylene protons. Scyllatoxin folds into a compact ellipsoidal shape. An alpha-helix (defined with 0.24 A resolution) spanning 2.5 turns from Leu5 till Ser14 is stabilized by Cys8-Cys26 and Cys12-Cys28 disulfide bridges to the carboxy-terminal strand of an anti-parallel beta-sheet. The antiparallel beta-sheet (defined at 0.66 A resolution) extends from Leu18 to Val29 with a tight turn at Gly23-Asp24 and displays a right-handed twist. Scyllatoxin competes with the toxins apamin from Apis mellifera mellifera and P05 from Androctonus mauretanicus mauretanicus for the same or similar high conductance calcium-activated potassium channels. Consideration of presently known biological activities and three-dimensional structures of these toxins suggest a different toxin-receptor interaction of scyllatoxin as compared to apamin and P05.
通过500兆赫的同核质子核磁共振方法，以1埃的分辨率测定了来自以色列金蝎毒液肽——海葵毒素（leurotoxin I）的三维溶液结构。数据分析和结构计算遵循DIANA及相关程序固有的常规方案，但有两个例外。首先，距离约束是通过先前描述的部分弛豫矩阵方法从二维核Overhauser谱中获得的。其次，由于六个半胱氨酸残基的配对模式并非预先确定，二硫键的明确归属完全是通过对初步DIANA结构的统计分析从核磁共振数据中实现的。在最终计算中，我们使用了227个上限距离约束、67个来自邻位耦合常数的扭转约束以及10个β-亚甲基质子的立体专一性归属。海葵毒素折叠成紧密的椭圆形。一个从Leu5到Ser14跨越2.5圈的α-螺旋（以0.24埃分辨率定义）通过Cys8-Cys26和Cys12-Cys28二硫键与反平行β-折叠的羧基末端链稳定相连。反平行β-折叠（以0.66埃分辨率定义）从Leu18延伸至Val29，在Gly23-Asp24处有一个紧密转角，并呈现右手扭转。海葵毒素与来自意大利蜜蜂的蜂毒明肽和来自摩洛哥杀人蝎的P05毒素竞争相同或相似的高电导钙激活钾通道。对这些毒素目前已知的生物活性和三维结构的考虑表明，与蜂毒明肽和P05相比，海葵毒素与受体的相互作用不同。
