EMBL, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
Fish Shellfish Immunol. 2012 May;32(5):724-31. doi: 10.1016/j.fsi.2012.01.021. Epub 2012 Feb 8.
Anti-lipopolysaccharide factors (ALFs) are the potent antimicrobial peptides that can bind and neutralize lipopolysaccharide (LPS). In this study, a new isoform of the ALF homologs (PtALF4) was cloned from eyestalk cDNA library of swimming crab Portunus trituberculatus. PtALF4 shared lower amino acid similarity with other ALFs, yet it contained the conserved LPS-binding domain and was clearly member of the ALF family. The genomic sequence of PtALF4 consisted of three exons interrupted by two introns. Several tandem repeats were found in both introns. Unlike most ALFs expressed in hemocytes, PtALF4 transcript was predominantly detected in eyestalk. After challenge with Vibrio alginolyticus, the temporal expression level of PtALF4 transcript in hemocytes showed a clear time-dependent response expression pattern with two significant peaks. The recombinant proteins of PtALF1, PtALF3 and PtALF4 revealed different antimicrobial activities against bacteria or fungus. These results together suggest that PtALF isoforms might be potent immune effectors to provide multiple protective functions against invading bacteria or fungus in P. trituberculatus.
抗脂多糖因子（ALFs）是一种强效的抗菌肽，能够结合并中和脂多糖（LPS）。在这项研究中，我们从三疣梭子蟹的眼柄 cDNA 文库中克隆到了一种新的 ALF 同源物（PtALF4）的异构体。PtALF4 与其他 ALFs 的氨基酸相似性较低，但它含有保守的 LPS 结合结构域，显然是 ALF 家族的成员。PtALF4 的基因组序列由三个外显子组成，由两个内含子隔开。两个内含子中都发现了几个串联重复序列。与大多数在血细胞中表达的 ALFs 不同，PtALF4 转录本主要在眼柄中检测到。在受到溶藻弧菌的刺激后，血细胞中 PtALF4 转录本的时间表达水平呈现出明显的时间依赖性反应表达模式，有两个显著的峰值。PtALF1、PtALF3 和 PtALF4 的重组蛋白显示出对细菌或真菌的不同抗菌活性。这些结果表明，PtALF 异构体可能是有效的免疫效应因子，为三疣梭子蟹提供了多种针对入侵细菌或真菌的保护功能。
