刚地弓形虫GRA25基因的克隆及序列分析

本研究旨在对来源于不同宿主和地理分布的22株弓形虫的GRA25基因进行PCR扩增并测序,对获得的GRA25基因序列进行比对,利用MP和ML两种方法对不同分离株的GRA25基因构建系统进化树。利用生物信息学软件将弓形虫RH株的GRA25基因翻译成氨基酸序列,对其编码蛋白的生物学特征进行分析。结果显示,弓形虫GRA25基因序列有2种长度,分别为939和948 bp。序列比对结果显示,GRA25基因在不同虫株间有82个核苷酸变异位点,变异率为0~4.4%。进化分析结果显示,用GRA25基因不能区分弓形虫基因Ⅰ型和Ⅱ型虫株。生物信息学分析预测弓形虫GRA25蛋白含有7个亲水区域,10个α-螺旋,3个β-折叠,8个无规则卷曲和8个潜在的线性B淋巴细胞抗原表位。本研究结果表明,GRA25基因不能作为标记分子区分不同基因型的弓形虫虫株,但可能作为疫苗候选分子研制新型抗弓形虫基因疫苗或表位肽疫苗。

Cloning and Sequence Analysis of Toxoplasma gondii GRA25 Gene

In this study,sequence variation of GRA25 genes among 22 Toxoplasma gondii (T.gondii) strains from different hosts and geographical locations were examined.The complete GRA25 genes from 22 T.gondii isolates were amplified,sequenced,and nucleotide variations were determined.Phylogenetic analysis among the different T.gondii isolates were conducted using maximum parsimony (MP) and maximum likelihood (ML) methods.The biological characteristics of the protein GRA25 of the T.gondii RH strain were predicted using bioinformatics software.The sequences of all the examined T.gondii strains were 939 or 948 bp in length.Sequence comparison of all 22 GRA25 sequences identified 82 variable nucleotide positions (0 to 4.4%).The results of phylogenetic analysis showed that strains belonging to the classical typeⅠand Ⅱ could not group into their own branches based on the GRA25 sequences.Bioinformatics analysis revealed that the protein GRA25 contained 7 hydrophobicity regions,10 alpha regions,3 beta sheets,8 random coils and 8 linear B-cell epitopes.These results suggested that the GRA25 gene was not an ideal genetic marker for population genetic study of T.gondii strains,but it might represent a good vaccine candidate against toxoplasmosis.