De Zoysa Mahanama, Kang Hyun-Sil, Song Young-Bo, Jee Youngheun, Lee Young-Don, Lee Jehee
Department of Marine Biotechnology, College of Ocean Science, Cheju National University, 66 Jejudaehakno, Ara-dong, Jeju, Jeju-Do 690-756, Republic of Korea.
Fish Shellfish Immunol. 2007 Jul;23(1):86-96. doi: 10.1016/j.fsi.2006.09.007. Epub 2006 Oct 4.
Myxovirus resistance (Mx) protein is one of the most studied antiviral proteins. It is induced by the type I interferon system (IFN alpha/beta) in various vertebrates, but its expression has not been identified or characterized in mollusks or other multi-cellular invertebrates to date. In this study, we isolated the Mx gene from a disk abalone (Haliotis discus discus) normalized cDNA library. Mx cDNA was sequenced, cloned and compared to other known Mx proteins. The full-length 1664 bp of abalone Mx cDNA contained a 1533-bp open reading frame that codes for 511 amino acids. Within the coding sequence of abalone Mx, characteristic features were found, such as a tripartite guanosine-5'-triphosphate (GTP)-binding motif and a dynamin family signature. In addition, leucine residues in the C-terminal region displayed a special leucine domain at L(468), L(475), L(489) and L(510), suggesting that abalone Mx may have a similar oligomerization function as other leucine zipper motifs. Abalone Mx protein exhibited 44% amino acid similarity with channel catfish Mx1, rainbow trout Mx2 and Atlantic halibut Mx. Abalones were injected intramuscularly with the known IFN inducer poly I:C and RT-PCR was performed for Mx mRNA analysis. The results showed enhanced Mx expression in abalone gill and digestive tissues 24h as well as 48 h after injection of poly I:C. Mx mRNA was expressed in gill, digestive gland, mantle and foot tissues in healthy abalone, suggesting that the basal level of Mx expressed is tissue-specific. There is no known Mx protein closely related to abalone Mx according to phylogenetic analysis. Abalone Mx may have diverged from a common gene ancestor of fish and mammalian Mx proteins, since abalone Mx showed high similarity in terms of conserved tripartite GTP-binding, dynamin family signature motifs and poly I:C enhancement of Mx mRNA expression.
黏液病毒抗性（Mx）蛋白是研究最多的抗病毒蛋白之一。它由多种脊椎动物的I型干扰素系统（IFNα/β）诱导产生，但迄今为止，在软体动物或其他多细胞无脊椎动物中尚未鉴定或表征其表达情况。在本研究中，我们从盘鲍（Haliotis discus discus）标准化cDNA文库中分离出Mx基因。对Mx cDNA进行了测序、克隆，并与其他已知的Mx蛋白进行了比较。盘鲍Mx cDNA全长1664 bp，包含一个1533 bp的开放阅读框，编码511个氨基酸。在盘鲍Mx的编码序列中，发现了一些特征性结构，如三联体鸟苷-5'-三磷酸（GTP）结合基序和发动蛋白家族特征。此外，C末端区域的亮氨酸残基在L(468)、L(475)、L(489)和L(510)处显示出一个特殊的亮氨酸结构域，表明盘鲍Mx可能具有与其他亮氨酸拉链基序相似的寡聚化功能。盘鲍Mx蛋白与斑点叉尾鮰Mx1、虹鳟Mx2和大西洋庸鲽Mx的氨基酸相似性为44%。给鲍鱼肌肉注射已知的IFN诱导剂聚肌胞苷酸（poly I:C），并进行RT-PCR分析Mx mRNA。结果显示，注射poly I:C后24小时和48小时，鲍鱼鳃和消化组织中的Mx表达增强。健康鲍鱼的鳃、消化腺、外套膜和足部组织中均表达Mx mRNA，表明Mx的基础表达水平具有组织特异性。系统发育分析表明，目前没有与盘鲍Mx密切相关的已知Mx蛋白。盘鲍Mx可能与鱼类和哺乳动物Mx蛋白的共同基因祖先发生了分化，因为盘鲍Mx在保守的三联体GTP结合、发动蛋白家族特征基序以及poly I:C对Mx mRNA表达的增强方面表现出高度相似性。
