大黄鱼Lcnkl3基因的分子结构、表达特征及多肽片段抗菌活性

作为重要的免疫基因, NK-lysin参与了鱼类非特异性免疫系统对抗病原感染的免疫应答过程。在之前的研究中, 我们已经发现重要经济鱼类大黄鱼(Larimichthys crocea)体内存在2种类型的NK-lysin基因。在本文中我们报道了1种新型大黄鱼NK-lysin基因Lcnkl3, 并对基因序列、表达特征及其多肽片段的抗菌活性进行了分析。Lcnkl3基因的开放阅读框长度为435 bp, 编码144个氨基酸残基, 其多肽序列Lcnkl3中包含Saposin B结构域及6个高度保守的半胱氨酸残基。系统进化分析表明Lcnkl3与大黄鱼Lcnkl2最为相似, 与其他鱼类NK-lysin多肽则差异较大。Lcnkl3基因在未受感染的大黄鱼各组织中具有不同的基础表达量, 表达水平最高的组织为心脏。在病原诱导的免疫应答过程中, Lcnkl3基因在各组织不同感染阶段的表达模式存在差异。源于Lcnkl3成熟肽序列的多肽片段对不同细菌的抑制和杀灭效果差异显著。以上结果表明Lcnkl3属于大黄鱼NK-lysin基因家族, 并参与了大黄鱼对抗病原感染的免疫过程。

Molecular structure, expression characteristics, and antibacterial activity of polypeptide fragment of Lcnkl3 in large yellow croaker

NK-lysin is an important immune gene involved in the non specific immune response against pathogen infection in teleosts. In previous studies, we found two types of NK-lysin genes in large yellow croaker (Lari­michthys crocea), a commercially important fish. Herein, we report the gene sequence, expression characteristics, and antibacterial activity of the polypeptide fragment in the novel NK-lysin gene Lcnkl3 of large yellow croaker. The open reading frame of Lcnkl3 was 435 bp in length and coded 144 amino acid residues; it contained a Saposin B domain and six highly conserved cysteine residues in its polypeptide sequence (Lcnkl3). Phylogenetic analysis showed that Lcnkl3 was most similar to Lcnkl2 in large yellow croaker but was quite different from other teleost NK-lysin polypeptide sequences. The Lcnkl3 gene exhibited different basic expression profiles in different tissues of uninfected large yellow croaker, and the expression was highest in the heart. The expression profiles of Lcnkl3 differed in different tissues and at different infection stages during the pathogen-induced immune response. The polypeptide fragment derived from the mature Lcnkl3 polypeptide sequence had different inhibitory and killing effects on different bacteria. These results indicate that Lcnkl3 belongs to the NK-lysin gene family and plays a role in the immune response of large yellow croakers during pathogen infection.