微孢子虫O-甘露糖糖基化通路相关酶基因序列的比较分析

糖蛋白在免疫识别、信号转导等生命进程中扮演重要角色。为研究微孢子虫糖蛋白及其糖基化类型,采用比较基因组学方法对微孢子虫O-甘露糖糖基化通路进行分析。真核生物的O-甘露糖糖基化通路中有6种主要酶类,包括己糖激酶、磷酸甘露糖酶、GDP甘露糖磷酸化酶、Dol-P甘露糖合成酶、甘露糖转移酶、Dol-P甘露糖蛋白甘露糖转移酶。通过生物信息学方法分析家蚕微孢子虫(Nosema bombycis)、蜜蜂微孢子虫(Nosema ceranae)、兔脑炎微孢子虫(Encephalitozoon cuniculi)、肠脑炎微孢子虫(Encephalitozoon intestinalis)、比氏肠道微孢子虫(Encephalitozoon bieneusi)和柞蚕微孢子虫(Nosema antheraea)的这6种酶基因编码氨基酸序列特征及结构域类型,发现这些酶的垂直同源基因比较保守,多重序列比对表明在6种微孢子虫之间,6种酶的氨基酸序列相似性比较高,系统进化分析显示同属的微孢子虫多聚为一簇。研究结果表明,N.bombycis、N.ceranae、E.cuniculi、E.intestinalis和N.antheraea 5种微孢子虫的O-甘露糖糖基化的蛋白质修饰通路是完整、保守的,然而在E.bieneusi中,其关键酶Dol-P甘露糖蛋白甘露糖转移酶的氨基酸序列比较短,只有342个氨基酸,缺失了关键结构域PMT,因此可能无法完成O-甘露糖糖基化修饰。以上微孢子虫的O-甘露糖糖基化通路中6种主要酶的序列信息,为后续解析家蚕微孢子虫糖基化通路及对糖蛋白糖基化类型与功能的研究提供了线索。

Comparative Analysis of Gene Sequences of Related Enzymes in O-mannosylation Pathway of Microsporidian

Glycoproteins play an importent role in immunological recognition,signal transduction and other biological processes.In order to study the glycoproteins and glycosylation patterns of microsporidia,O-mannosylation pathway of microsporidia was analyzed using a comparative genomic approach.In eukaryotes,major enzymes involved in the O-mannosylation pathway are hexokinase,phosphomannomutase,GDP mannose phosphorylase,Dol-P mannose-synthase,mannosyltransferase and Dol-P mannose protein mannosyltransferase.Through bioinformatic analysis on the amino acid sequence features and domain types of these six enzyme-encoding genes in six microsporidian species,namely Nosema bombycis,Nosema ceranae,Encephalitozoon cuniculi,Encephalitozoon intestinalis,Encephalitozoon bieneusi and Nosema antheraea,it was found that the vertical homologous genes of these enzymes are well conserved.Multiple sequence alignment revealed that the six enzymes share a high sequence identity between six microsporidian species.Phylogenetic analysis showed that enzymes from microsporidian species of the same genus form a monophyletic clade.Sequence analysis also showed that O-mannosylation pathway is complete and conserved in N.bombycis,N.ceranae,E.cuniculi,E.intestinalis and N.antheraea.However,Dol-P mannose protein mannosyltransferase,the key enzyme in O-mannosylation pathway,is truncated in E.bieneusi.It has only 342 amino acids and lacks the key functional domain PMT,suggesting that E.bieneusi is not able to complete O-mannosylation modification process.The obtained sequence information of the six major enzymes involved in O-mannosylation pathway in six microsporidian species provides a valuable clue for further studies on glycosylation pathway and on glycosylation types and functions of glycoprotein in N.bombycis.