沙蝰蛇毒磷脂酶A_2分子进化特征的研究

A STUDY ON THE PROPERTIES OF MOLECULAR EVOLUTION OF PHOSPHOLIPASE A_2 FROM VIPERA AMMODYTES AMMODYTES VENOM

目的 :了解沙蝰蛇毒 PL A2 分子在进化过程中的特点 ,特别是基因水平上的特点。方法 :采用不加权成对群算术平均法( UPGMA)构建来自沙蝰蛇毒的 5种 PL A2 的分子进化树 ;将 PL A2 c DNA顺序中编码区内的碱基进行两两比较 ,统计和分析编码氨基酸密码的三个碱基不同位置的取代数及同义取代 ( S)和非同义取代 ( N )数目 ;并分别统计和分析这些 PL A2 的二联碱基胞嘧啶 -鸟嘌呤 ( Cp G)和鸟嘌呤 -胞嘧啶 ( Gp C)的数目及分布情况。结果 :1成功地构建了与 PL A2 性质、功能和彼此间关系相符的分子进化树 ;2碱基取代以第 、 位为多 ,同义取代的数目也远低于非同义取代的数目 ,S/ N远小于 1;3编码区内的二联碱基顺序 Cp G出现的频率非同寻常的高 ,Gp C/ Cp G之比为 1.12～ 1.2 5。非编码区内 Cp G则明显受到压抑而数目很少。结论 :沙蝰蛇毒的 PL A2 基因有加速进化的情况发生 ,可能与其基因中异常高的 Cp

Objective:To understand the properties of molecular evolution of phospholipase A 2 (PLA 2) from vipera ammodytes ammodytes venom,particular in gene levelMethods:The evolutionary tree was constructed by unweighted pairgroup method with arithmetic mean (UPGMA) based on the nucleotide substitutionsWe made a comparison of the nucleotide sequences between these PLA 2 in pairs in the coding regionsThe numbers of base substitution in the codon for each position (first,second,and third) and those synonymous substitutions and nonsynonymous substitutions were calculated and analyzedWe also calculated and analyzed the numbers and distribution of the CpG and GpCResults:①The molecular evolutionary tree of PLA 2 was constructed successfullyThe tree corresponded to their properties,function and relationship;② The numbers of the base substitution at first and second positions were more than that at third positionThe numbers of nonsynonymous substitution were much greater than that of synonymous substitutionsThe ratios of synonymoustononsynonymous substitution were lower than 1;③The frequency of the dinucleolide CpG in the protein-coding region sequences was unusually high,the ratios of GpC to CpG were from 112 to 125In the untranslated region sequences (5' and 3'),the frequencies of the CpG were markedly depressedConclusions:The evolution of phospholipase A 2 genes from vipera ammodytes ammodytes was acceleratedAccelerated evolution might relate to high frequency of dinucleolide CpG in the genes