稻瘟病菌一个假定的α-1，2-甘露糖苷酶生物信息学分析

Bioinformatic analysis of a putative 1,2-alpha-mannosidase in Magnaporthe grisea

对稻瘟病菌一个假定的α-1,2-甘露糖苷酶MgManⅠ生物信息学进行分析的结果表明,该蛋白与海枣曲霉、桔青霉等丝状真菌的已知α-1,2-甘露糖苷酶(EC 3.2.1.113)氨基酸序列具有高度同源性,并具有其相同的活性中心位点.基序分析表明,该蛋白可能含有4个N-糖基化位点、3类19个磷酸化位点和12个N-肉豆蔻酰位点.该蛋白的相对分子质量预测为58.2 ku,理论等电点pI为5.17,并且为细胞外分泌蛋白,信号肽剪切位点为21A和22S之间.系统发育分析表明:MgManⅠ与丝状真菌中的海枣曲霉、桔青霉α-1,2-甘露糖苷酶之间亲缘关系最近,形成一大类;动物的α-1,2-甘露糖苷酶与植物的α-1,2-甘露糖苷酶分别聚成二大类;酿酒酵母α-1,2-甘露糖苷酶ScManⅠ与丝状真菌不同,单独成为一类.进一步以已知结构的PcManⅠ为模板,通过同源建模得到的三维结构图形基本反映了MgManⅠ的空间构象,为深入研究该蛋白的生化特性和生物学功能奠定了基础.

The bioinformatic tools were used to analyze a hypothetical 1,2-alpha-mannosidase （MgMan Ⅰ ） of Magnaporthe grisea. The results showed that the MgMan I is highly homologous to known 1,2-alpha-mannosidase （ EC 3.2.1.113） protein from filamentous fungi such as Aspergillus phoenicis and Penicillium citrinum, with the same activity center sites. Motif analysis showed that the protein may contain 4 N-glycosylation sites, 19 phosphorylation sites and 12 N-myristoylation sites. The protein is predicted to have a signal cleavage site between 21A and 22S, and be secreted to extracellular compartments, with a relative molecular weight of 58.2 ku. The predicted pI value is 5.17. Phylogenetic analysis showed that the evolutionary distance was the closest between MgMan Ⅰ and 1,2-alpha-mannosidases from filamentous fungi, such as P. citrinum and A. phoenicis, which were clustered in the same clade, distinguishing from animal clade and plant clade. Interestingly, 1,2-alpha-mannosidase from Saccharomyces cerevisiae forms a unique clade different from the filamentous fungus clade. The three-dimensional structural graphic was also constructed via homologous modeling based on the known structure of PcMan Ⅰ , which well reflects the space conformation of MgMan Ⅰ. In conclusion, the results of the bioinformatic analysis will facilitate to understand the structure and function of this putative 1,2-alpha-mannosidase in the fungus.