【作者】 李恩； 吴孝兵； 晏鹏； 史燕；

【Author】 LI En WU Xiao-Bing YAN Peng SHI Yan (College of Li fe Sciences ,Anhui Normal University, Wuhu 241000 ,China)

【机构】 安徽师范大学生命科学学院；

【摘要】 利用一对简并性引物扩增了中国石龙子(Eumeces chinensis)MHC Ⅱ类分子B 基因第二外元的部分片段,并对PCR产物进行了克隆和测序,结果得到7种长度为166 bp的不同序列,序列中有12个变异位点,核苷酸的非同义替换多于同义替换,造成8 个氨基酸的改变。氨基酸序列中假定的抗原结合位点的交异明显高于非抗原结合位点,表明这些变异位点负责识别和呈递不同的抗原。核苷酸序列与其他物种MHC同源序列的聚类分析结果与其系统进化基本相符,并同氨基酸序列分析相一致。同一个体中发现有多种序列,提示中国石龙子MHCⅡ类分子B基因可能存在着座位重复。更多还原

【Abstract】 The major histocompatibility complex (MHC) ,with the highest genetic polymorphism,is a cluster of genes involved in immune response regulation in the vertebrates. Here we examined variation at a class Ⅱ MHC B gene in Eumeces chinensis. A pair of degenerate primers was used to amplify 166 bp fragments at exon 2 of the class Ⅱ MHC B gene. PCR products were cloned into a pGEM-T Vector after purification. Seven different sequences were obtained from cloning and sequencing. All seven sequences did not show deletions, insertions, or stop codons, and therefore could be assumed functional in vivo. There were 12 variable sites in the nucleotide sequences, the ratio of nonsynony-mous substitutions was higher than that of synonymous substitutions (dN/ds = 2. 762/0. 857), which caused 8 amino acid differences. The variation of putative antigen-binding site was much higher than that of nonantigen-binding site, suggesting that the variation at these sites would be responsible for recognition and presentation of different kinds of antigens. Phylogenetic relationship of seven nucleotide sequences and other species MHC class Ⅱ gene constructed using the neighbor-joining (NJ) method in MEGA and maximum parsimony (MP) method in PAUP 4. 0 reflected the evolutionary relationships among species, and accorded with homologous analysis of amino acid sequences. More than two sequences were found in the same individual, indicating there would be locus duplication in the class Ⅱ major histocompatibility complex B gene of Eumeces chinensis.更多还原