哺乳动物Gpx基因家族进化选择和功能分歧研究

Evolutionary Selection and Functional Divergence of Gpx Gene Family in Mammals

研究哺乳动物谷胱甘肽过氧化物酶基因家族(Gpx)的亲缘关系和进化选择压力性质。从NCBI等网站获取哺乳动物Gpx基因编码区核酸序列和GPX蛋白氨基酸序列,并用MEGA、Clustal构建亲缘关系树,用SignalP和TargetP分析信号肽和亚细胞定位信息;用K estimator和PAML分析其Gpx基因家族进化先后顺序和选择压力;用Diverge分析GPX蛋白家族功能分歧。结果表明,GPX蛋白家族进化中形成两个亚类,其一包括GPX1和GPX2,其二包括GPX3、GPX5和GPX6;各GPX蛋白成员均有高度保守的GPX蛋白家族基序和高度保守的硒代半胱氨酸或半胱氨酸残基,氨基端信号肽分析显示,GPX1蛋白为胞浆线粒体型,其余家族成员均为胞外分泌型;哺乳动物Gpx1基因进化上受到严格的负选择作用,Gpx基因家族成员保守区也受到负选择作用,但用枝位点模型却检出了正选择作用,GPX蛋白家族内存在轻微的功能分歧。哺乳动物GPX蛋白家族的进化上的负选择作用表明其在哺乳动物清除自由基抗氧化方面的关键作用。

This paper studys the phylogenetic relationship and evolutionary selective pressure of Gpx gene family in mammals. And we collect CDS and protein sequence of Gpx genes from NCBI and construct phylogenetic tree with MEGA and Clustal, identify signal pep- tide and subcelluar localization with SignalP and TargetP respectively, conduct evolutionary＂ analysis with K estimator and PAML, ana- lyze functional divergence with diverge. There are two subclasses, GPX1, GPX2 and GPX3, GPX 5, GPX 6 in the protein family ; all members share highly conserved token amino acid sequence of GPX family, as well as the same highly conserved amino acid Sec or Cys. Analysis of the signal peptides in the N-termini indicates that GPX1 protein was mitochondrion-localized while all the other mem- bers were guided outside cells. Both human Gpx gene family and mammalian Gpxl genes have endured negative selection, however, positive seleetion was examined in human Gpx gene family when using the branch-site model in PAML and there are slight functional di- vergence in human GPX protein family. The high conservation and evolutionary purified selection of mammalian Gpx gene family imply their essential roles in scavenging free radicals.