摘要
CD4基因是质膜上的转运系统之一,为动物辅助性T细胞(TH)和部分胸腺细胞的共受体与信号传导分子,参与TCR介导的TH细胞活化和胸腺细胞分化过程.该研究首次克隆了山羊CD4基因(GenBank登录号:EU913093),并分析了该基因的组织表达情况.结果表明:所克隆的山羊CD4全长cDNA序列为1 555bp,开放阅读框(ORF)为1 368bp,编码455个氨基酸的蛋白,相对分子质量为5.05×104,等电点为9.52.山羊CD4蛋白前体由信号肽、胞外区、跨膜区和胞浆区4个部分构成.胞外区含有4个Ig样结构域,2个二硫键(C41—C109和C143—C180)及3个N糖基化位点(N231,N263和N343).氨基酸序列比对表明山羊CD4与绵羊CD4的氨基酸相似性为98%,与猪、人、兔、狗、猫、蝙蝠以及小鼠的氨基酸相似性分别为81%,74%,73%,72%,70%,70%和66%.系统发育树表明山羊CD4与绵羊和猪的CD4蛋白聚成一支,表明它们有较近的亲缘关系,其中山羊与绵羊的亲缘关系最近,而与狗、蝙蝠、兔、人和小鼠的亲缘关系相对较远.实时荧光定量PCR分析发现,CD4在山羊淋巴中的表达量最高,在睾丸中表达量较低,表明山羊CD4是一种免疫分子.
CD4 is one of the transport factors on the cell membrane functioning as an important co-receptor and signal molecule expressed on the surface of T help cells（TH） and thymocytes.CD4 is involved in the activation of peripheral T help cells and the differentiation of thymocytes.In this study,we cloned the goat CD4 gene（GenBank ID： EU913093） and analyzed its expression in different tissues.Sequence analysis showed that the full-length CD4 cDNA was 1 555 nt,containing an open reading frame（ORF） of 1 368 nt.It encodes a polypeptide of 455 amino acids,which is 50.50 kD in the molecular weight and is 9.52 as the isoelectric point.The goat CD4 precursor protein composes of signal peptide,extracellular region,transmembrane domain and cytoplasmic domain.The extracellular region contains four immunoglobulin-like domains,two disulfide bonds（C41—C109 and C143—C180） and three N-glycosylation sites（N231,N263 and N343）.Alignment of the deduced amino acid sequences showed that goat CD4 has a high similarity（98%） with that of sheep,and has 81%,74%,73%,72%,70%,70% and 66% similarity with pig,human,rabbit,dog,cat,bat and mouse CD4,respectively.Phylogenetic analysis showed that goat CD4 forms a cluster with sheep and pig CD4,suggesting a fairly close relationship between them.The relationship between goat and sheep is the closest,while the relationship of goat with dog,bat,rabbit,human and mouse is relatively distant.Real time PCR revealed the expression level of CD4 is the highest in lymph and relatively low in testis is,suggesting that goat CD4 is an immune molecule.
出处
《西南大学学报（自然科学版）》
CAS
CSCD
北大核心
2012年第2期1-8,共8页
Journal of Southwest University(Natural Science Edition)
基金
国家自然科学基金资助项目(30600430)
