This study was undertaken on three species of rabbitfish, Siganus puellus, Siganus unimaculatus, and Siganus virgatus, to clarify whether stonefish toxin-like toxins are distributed in rabbitfish. The primary structures of toxins from these three species of rabbitfish were successfully elucidated by complementary DNA cloning and found to comprise two different subunits with almost the same molecular mass, i.e., 70–80 kDa. Based on the heterodimeric structure, molecular size, and amino acid sequence features, the toxins from the three species of rabbitfish were judged to be analogues of the stonefish toxins. The amino acid sequences of the toxins from S. puellus and S. unimaculatus were very similar, and distinguishable from those of S. virgatus and S. fuscescens. Homology modeling indicated that the predicted three-dimensional structures of the rabbitfish toxins are comparable to that of stonustoxin (a toxin of the stonefish Synanceia horrida), as they are composed of four domains. It is thus assumed that the rabbitfish toxins form pores in cell membranes by essentially the same mechanism as stonustoxin, although the rabbitfish toxins have alterations of some amino acid residues that are suggested to be critical for the interaction between the two subunits of stonustoxin.

中文翻译：

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来自三种兔鱼 Siganus puellus、Siganus unimaculatus 和 Siganus virgatus 的石鱼毒素样毒素的初级结构和构象

本研究对三种比目鱼（Siganus puellus、Siganus unimaculatus 和Siganus virgatus）进行了研究，以阐明石鱼毒素样毒素是否分布在比目鱼中。来自这三种兔鱼的毒素的主要结构通过互补 DNA 克隆成功阐明，发现包含两个不同的亚基，具有几乎相同的分子量，即 70-80 kDa。根据异二聚体结构、分子大小和氨基酸序列特征，三种兔鱼的毒素被判断为石鱼毒素的类似物。S. puellus 和 S. unimaculatus 毒素的氨基酸序列非常相似，可与 S. virgatus 和 S. fuscescens 的毒素氨基酸序列区分开来。同源性建模表明，兔鱼毒素的预测三维结构与石鱼毒素（石鱼 Synanceia horrida 的一种毒素）的三维结构相当，因为它们由四个结构域组成。因此假定兔鱼毒素通过与石斑鱼毒素基本相同的机制在细胞膜中形成孔，尽管兔鱼毒素具有一些氨基酸残基的改变，这些氨基酸残基被认为对石斑鱼毒素的两个亚基之间的相互作用至关重要。