Zhu S, Li W, Jiang D, Zeng X
Department of Biotechnology, College of Life Sciences, Wuhan University, China.
IUBMB Life. 2000 Jul;50(1):57-61. doi: 10.1080/15216540050176601.
Insect defensin refers to a group of antibacterial peptides derived from a variety of insect species as well as from scorpion and possessing a three-dimensional structure highly similar to that of scorpion toxins. A full-length cDNA encoding an insect defensin-like peptide was isolated from the venom gland cDNA library of the Chinese scorpion Buthus martensii Karsch. The precursor, the overall organization of which is similar to that of insect defensins, consists of 61 amino acid residues with a putative signal peptide of 15 residues, a propeptide of 7 residues, and a mature peptide of 39 residues (named BmTXKS2). The positions of six cysteines and a conserved glycine in mature BmTXKS2 are the same as those in LqDef, the first defensin found in scorpions, which suggests these peptides should present a similar cysteine-stabilized alphabetamotif. Phylogenetic analysis further shows that the structure of BmTXKS2 is closer to that of ancient defensins (e.g., LqDef and AaDef, two insect defensins present in the scorpion hemolymph) than to scorpion toxins.
昆虫防御素是指一类源自多种昆虫以及蝎子的抗菌肽，其三维结构与蝎毒素高度相似。从东亚钳蝎（Buthus martensii Karsch）的毒腺cDNA文库中分离出了一个编码昆虫防御素样肽的全长cDNA。该前体的整体结构与昆虫防御素相似，由61个氨基酸残基组成，其中有一个15个残基的假定信号肽、一个7个残基的前肽和一个39个残基的成熟肽（命名为BmTXKS2）。成熟的BmTXKS2中六个半胱氨酸和一个保守甘氨酸的位置与蝎防御素LqDef（蝎子中发现的首个防御素）中的相同，这表明这些肽应呈现相似的半胱氨酸稳定的α基序。系统发育分析进一步表明，BmTXKS2的结构与古代防御素（如LqDef和AaDef，蝎子血淋巴中存在的两种昆虫防御素）的结构比与蝎毒素的结构更接近。
