人瘦素蛋白的序列特征分析及蛋白-蛋白相互作用网络构建

Analysis of sequence characteristic of human leptin protein and the establishment of protein-protein interaction network

目的探讨人瘦素(leptin)蛋白序列特征并构建蛋白-蛋白相互作用(PPI)网络。方法利用Expasy在线数据分析服务器、TMHMM-2.0在线网站、SOPMA二级结构预测分析软件、STRING数据库、分子进化遗传分析7.0软件等生物信息学分析工具,对人leptin蛋白的理化性质、结构、PPI网络、系统进化树进行分析。结果人leptin蛋白含有167个氨基酸残基,分子式为C_(842)H_(1333)N_(217)O_(245)S_(7),相对分子质量约为18640.57,理论等电点为5.88,不稳定系数为47.52,平均亲水系数为0.131;人leptin蛋白氨基端具有信号肽,属于分泌蛋白,含有磷酸化位点,是主要存在于细胞外的亲脂蛋白。人leptin蛋白二级结构主要以α-螺旋为主(占57.49%),其次为不规则卷曲(占32.34%)、延伸链(占7.78%)和β转角(占2.4%),其三级结构与二级结构预测结果相似,且与模板序列的相似度高达99.32%。PPI网络显示,与人leptin蛋白发生相互作用的蛋白家族包括LEPR、GHRL、GCG、IAPP、PPARG、STAT3、SOCS3、JAK2、NPY、PTPN1。系统进化树结果表明,人leptin蛋白与黑猩猩的亲缘关系较近。结论人leptin蛋白具有信号肽结构,属于非糖基化分泌型蛋白,且可能与LEPR、GHRL、GCG、IAPP、PPARG、STAT3、SOCS3、JAK2、NPY、PTPN1蛋白存在互作关系,其蛋白表达水平在外周血循环系统中的变化可能导致免疫功能紊乱。

Objective To explore the sequence characteristic of human leptin protein and to establish protein-protein interaction(PPI)network.Methods The bioinformatic analysis tools in terms of Expasy online data analyzer,TMHMM-2.0 online website,SOPMA secondary structure prediction method,STRING database,and Molecular Evolutionary Genetics Analysis 7.0 software,etc.,were used to analyze physico-chemical property,structure,PPI network,phylogenetic tree on human leptin protein.Results Human leptin protein contained 167 amino acid residues,its molecular formula was C_(842)H_(1333)N_(217)O_(245)S_(7),its relative molecular mass was around 18640.57,its theoretical isoelectric point was 5.88,its instability coefficient was 47.52,and its average hydrophilic coefficient was 0.131.Amino terminal of human leptin protein possessed signal peptide,which belonged to secreted protein and contained phosphorylated locus,and was lipoprotein existed mainly in extra cell.Secondary structure of human leptin protein was mainlyα-helix(accounting for 57.49%),followed by irregular crimp(accounting for 32.34%),extended chain(accounting for 7.78%),andβrotation(accounting for 2.4%);moreover,its tertiary structure exhibited similar prediction results with the secondary structure,and the similarity to the template sequence reached up to 99.32%.The PPI network revealed that protein family interacting with human leptin protein contained LEPR,GHRL,GCG,IAPP,PPARG,STAT3,SOCS3,JAK2,NPY,and PTPN1.The results of phylogenetic tree indicated that human leptin protein was closely related to Pan troglodytes.Conclusion Human leptin protein possesses structure of signal peptide,which belongs to non-glycosylated secreted protein,and may interact with LEPR,GHRL,GCG,IAPP,PPARG,STAT3,SOCS3,JAK2,NPY,and PTPN1 proteins;in addition,the change of its protein expression in peripheral blood circulation system may lead to immune dysfunction.