花粉变应原的分类和相关的进化分析

目的 分析各种花粉变应原所属的蛋白家族,统计各类蛋白作为变应原出现的次数和在各科植物间的分布情况,结合进化树分析,以了解花粉变应原在自然界分布的一般规律.方法 通过NCBI数据库获取目前已知的所有变应原.用批处理(Batch Entrez)获得全部的氨基酸序列.将每个序列与Pfam数据库比对,以确定各种花粉变应原所属的蛋白家族.对成员众多的Profilin、Ex-pansin家族,应用BLAST搜索变应原的同源序列,获取序列号,Batch Entrez获得全部的氨基酸序列,最后用MEGA4.0软件生成进化树.结果 目前已知的168个花粉变应原,分属于26个蛋白家族.其中,Profilin、pollen_allerg_1和EF hand是3种成员最多的变应原家族,分别有25、20、19种变应原,占总数的38%.10个排名靠前的蛋白家族,变应原数量占总数的79%.在花粉变应原家族中,既有Profilin般分布广泛的,几乎涉及所有的科;也有局限于某科植物的如Ribonuclease、FAD_binding pro-tein、Amb_V、Thaumatin等.通过进化分析可知,各种Profilin变应原高度同源,变应原序列在不同物种间具有高度保守性.禾本科花粉的β-Expansin与无变应原性的Expansin分开进化.结论 通过对花粉变应原的蛋白家族分类,可为变态反应学的基础研究、过敏性疾病的临床诊疗提供参考,并有助于快速发现新的致敏物种和新的变应原.Profilin的高度保守性可能是交叉反应(cross reactivity)发生的主要原因之一.

Classification and evolutionary analysis of pollen allergens

Objective To classify all the plant pollen allergens, each allergen sequence available was compared with protein family database. After that, the appearance and taxonomic distribution of each protein family could be known. When made reference to evolutionary analysis, a regular rule of the distribu-tion of all plant pollen allergens could be concluded. Methods Protein family memberships of each allergen were assigned by comparing the sequences with the Pfam database. Representative members of the most a-bundant pollen allergen families were compared with the Uniprot database using the BLAST server. Acces-sion number of all the interesting homologous could be obtained and all the sequence information could be ac-quired by Batch Entrez. Finally, the evolutionary trees were drawn with the help of MEGA4.0 software. Re-sults One hundred and sixty-eight pollen allergens were classified into 26 protein families. Profilins, pollen _allerg_1 and EF hands constituted the most abundant pollen allergen families. Profilins and EF hands oc-curred in almost all allergenic plant families, whereas allergenic Expansins, FAD_binding proteins, Amb_V allergens and Thaumatins were confined to single taxon. Conclusion It is concluded that the highly con-served sequences of allergens families such as Profilin may be one of the most important reasons of the cross reactivities in allergic diseases. The classification of pollen allergens may be helpful to clinical practice and basic research.