Kem W R, Dunn B M
Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville 32610.
Toxicon. 1988;26(11):997-1008. doi: 10.1016/0041-0101(88)90198-5.
A basic protein cytolysin previously isolated from the Caribbean sea anemone Stichodactyla helianthus was shown by CM cellulose chromatography to consist of four isotoxins possessing different N-terminal amino acid sequences. These are designated as toxins I-IV in order of increasing isoelectric point. The estimated molecular sizes (17,400-18,200) of toxins I-III were very similar; toxins I and II posses one additional amino acid at their amino terminus relative to toxin III. Under denaturing conditions, toxin IV behaved as a significantly larger (19,600) polypeptide; Edman sequencing established that it possesses a seven residue extension at the N-terminal end relative to toxin III. None of the variants contained half-cystines or reducing sugars. Toxin III contributed 83% of the total purified cytolytic (hemolytic) activity, toxin II 14%, and the relatively insoluble toxins I and IV together only contributed about 3% of the total cytolytic activity. Cytolysin III lysed Ehrlich ascitic tumour cells, but when administered intraperitoneally in nonlethal doses to mice already inoculated with this tumour, it failed to protect the mice against the tumour. Comparison of the partial amino acid sequence of equinatoxin, another sea anemone protein cytolysin, with that of Stichodactyla cytolysin III indicates they are highly homologous. Many other cytolytic proteins isolated from sea anemones share these properties with Stichodactyla cytolysins: (1) selective inhibition of hemolytic activity by preincubation with sphingomyelin, (2) a molecular size of 10,000-20,000, and (3) an isoelectric point of 9 or above.
先前从加勒比海海葵太阳花海葵中分离出的一种碱性蛋白质溶细胞素，经CM纤维素色谱分析表明，它由四种具有不同N端氨基酸序列的同毒素组成。这些按等电点递增顺序被命名为毒素I-IV。毒素I-III的估计分子大小（17,400-18,200）非常相似；相对于毒素III，毒素I和II在其氨基末端多一个氨基酸。在变性条件下，毒素IV表现为一种明显更大（19,600）的多肽；埃德曼测序确定它相对于毒素III在N端有一个七个残基的延伸。这些变体均不含半胱氨酸或还原糖。毒素III占总纯化溶细胞（溶血）活性的83%，毒素II占14%，相对不溶的毒素I和IV总共仅占总溶细胞活性的约3%。溶细胞素III能裂解艾氏腹水瘤细胞，但当以非致死剂量腹腔注射给已接种该肿瘤的小鼠时，它未能保护小鼠免受肿瘤侵害。将另一种海葵蛋白质溶细胞素海葵毒素的部分氨基酸序列与太阳花海葵溶细胞素III的序列进行比较，表明它们高度同源。从海葵中分离出的许多其他溶细胞蛋白与太阳花海葵溶细胞素具有这些共同特性：（1）与鞘磷脂预孵育可选择性抑制溶血活性，（2）分子大小为10,000-20,000，（3）等电点为9或更高。
