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目的 克隆奶牛乳腺炎无乳链球菌菌毛岛屿BP基因片段并进行序列分析. 方法 根据GenBank已公布牛源无乳链球菌菌毛岛屿PI-2a的BP基因序列,采用Primer 5.0软件设计1对特异性引物,以内蒙古通辽地区分离的乳源性无乳链球菌临床菌株总DNA为模板PCR扩增BP基因片段,并进行生物信息学分析. 结果 克隆的BP基因序列大小为609bp,编码203个氨基酸残基,其基因序列与GenBank上公布的牛源无乳链球菌菌毛岛屿PI-2a的BP基因(EU930008)相似性为100％.菌毛岛屿骨架蛋白BP二级结构的a螺旋在N端分布较多;β折叠较丰富,且分布于C端较多;无规则卷曲分布较均匀.菌毛岛屿骨架蛋白BP的亲水区分布较广,遍布于整个多肽区,属于亲水性蛋白.BP蛋白分子表面可及性较高,区域占比达57.0％,且抗原性较好. 结论 奶牛乳腺炎无乳链球菌菌毛骨架蛋白BP基因具有高度保守性,其编码蛋白具有良好的抗原性,可作为防治无乳链球菌性乳腺炎的候选抗原序列.“,”Objective To clone and analyze the antigenicity of a fragment of a gene that codes for a pilus backbone protein (BP) in Streptococcus agalactiae causing mastitis in dairy cattle.Methods The software Primer 5.0 was used to design a pair of specific primers in accordance with the sequence of an S.agalactiae gene that codes for pilus backbone protein (BP) PI-2a published in GenBank.Total DNA from clinical isolates of S.agalactiae isolated from cattle with mastitis in the Tongliao area of Inner Mongolia served as a template,and a fragment of the BP gene was amplified with PCR and analyzed bioinformatically.Results The amplified BP gene sequence was 609 bp in length and it encoded 203 amino acids.This gene sequence had 100％ similarity to the pilus BP gene of bovine S.agalactiae coding for PI-2a (EU930008) published in GenBank.α-helices of the secondary structure of the pilus BP were often located at the N-terminus;β-folds were abundant and often located at the C-terminus.Random coils were evenly distributed throughout the structure.The pilus BP had widely distributed hydrophilic regions throughout a polypeptide segment,so the protein is hydrophilic.Protein molecules have a high surface accessibility,accounting for as much as 57.0％ of the surface,and good antigenicity.Conclusion The BP gene of S.agalactiae is highly conserved,and the protein it codes for has good antigenicity.This protein can be used as a potential antigen sequence for control of S.agalactiae causing mastitis.