Tamiya N, Abe H
Biochem J. 1972 Nov;130(2):547-55. doi: 10.1042/bj1300547.
Erabutoxin c, a minor neurotoxic component of the venom of a sea snake Laticauda semifasciata, was isolated in pure form by repeated column chromatography on CM-cellulose columns. The toxin was crystallizable and monodisperse in rechromatography, disc electrophoresis and isoelectric focusing (isoelectric point, pH9.23-9.25). The molecular weight of the toxin, as estimated by gel filtration, was 7000. The toxin showed the same lethal activity to mice (0.13mug/g body wt., intramuscular injection) and the same effect on isolated frog muscle as erabutoxins a and b, the main toxic components of the venom. The toxin inhibited the acetylcholine contracture but not the potassium chloride contracture of muscle. Erabutoxin c consisted of 62 amino acid residues, containing one fewer lysine and one more histidine than erabutoxin a and one fewer lysine and one more aspartic acid (or asparagine) than erabutoxin b. Erabutoxin c was reduced, S-carboxymethylated and hydrolysed with trypsin. The only fragment different from the corresponding fragments from erabutoxin b was hydrolysed further with pepsin. One of the peptic fragments, which was assumed to have the aspartic acid (or asparagine) residue in question at the C-terminal end, was treated with carboxypeptidase A. The C-terminal residue was found to be an asparagine. It was therefore concluded that erabutoxin c was [51-asparagine]-erabutoxin b.
海蛇半环扁尾海蛇毒液中的一种次要神经毒性成分—— erabutoxin c，通过在CM - 纤维素柱上反复进行柱色谱法被分离成纯品。该毒素在再色谱、圆盘电泳和等电聚焦（等电点，pH9.23 - 9.25）中可结晶且呈单分散状态。通过凝胶过滤估算，该毒素的分子量为7000。该毒素对小鼠的致死活性（0.13微克/克体重，肌肉注射）以及对离体蛙肌的作用与该毒液的主要毒性成分—— erabutoxins a和b相同。该毒素抑制肌肉的乙酰胆碱挛缩，但不抑制氯化钾挛缩。Erabutoxin c由62个氨基酸残基组成，与erabutoxin a相比，赖氨酸少一个，组氨酸多一个；与erabutoxin b相比，赖氨酸少一个，天冬氨酸（或天冬酰胺）多一个。Erabutoxin c经还原、S - 羧甲基化并经胰蛋白酶水解。与erabutoxin b相应片段不同的唯一片段再用胃蛋白酶进一步水解。假定在C末端有上述天冬氨酸（或天冬酰胺）残基的一个胃蛋白酶片段用羧肽酶A处理。发现C末端残基是天冬酰胺。因此得出结论，erabutoxin c是[51 - 天冬酰胺] - erabutoxin b。
