Menez A, Bouet F, Tamiya N, Fromageot P
Biochim Biophys Acta. 1976 Nov 26;453(1):121-32. doi: 10.1016/0005-2795(76)90256-7.
alpha-Neurotoxin from Naja nigricollis and erabutoxin b from Laticauda semifasciata, two homologous neurotoxic proteins, are studied by circular dichroism, ultraviolet spectroscopy and fluorescence in various water/trifluoroethanol mixtures. The data obtained show that the beta structure of alpha-neurotoxin is conserved in water as well as in the organic solvent. By contrast, erabutoxin b changes from the beta-structure in water to the helix type in trifluoroethanol. The latter induces similarly for both toxins a structural modification around tryptophan 29, a residue common to all neurotoxins known to date. The vicinity of tyrosine 25, another common amino acid, is also altered by the presence of the organic solvent as demonstrated by the sudden increase of reactivity of the phenolic ring towards iodine. The present work affords some evidence for the presence of a particular structure located around the two aromatic residues, which is common to all neurotoxins and able to rearrange independently from the rest of the molecule. Biological importance of this peculiar region is highly probable.
对两种同源神经毒性蛋白——黑颈眼镜蛇的α-神经毒素和半环扁尾海蛇的海蛇毒素b，在各种水/三氟乙醇混合物中通过圆二色性、紫外光谱和荧光进行了研究。所获得的数据表明，α-神经毒素的β结构在水中和有机溶剂中均得以保留。相比之下，海蛇毒素b则从水中的β结构转变为三氟乙醇中的螺旋结构。对于这两种毒素，后者均会在色氨酸29周围诱导一种结构修饰，色氨酸29是迄今为止所有已知神经毒素共有的一个残基。另一个常见氨基酸酪氨酸25附近的区域，也会因有机溶剂的存在而发生改变，这可通过酚环对碘的反应性突然增加得以证明。目前的研究工作为所有神经毒素共有的、位于两个芳香族残基周围的一种特定结构的存在提供了一些证据，该结构能够独立于分子的其余部分进行重排。这一特殊区域的生物学重要性极有可能存在。
