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目的 获得通辽地区奶牛乳腺炎致病菌无乳链球菌相关菌毛岛屿BP基因序列并进行比对分析. 方法 根据DNAMAN分析基因库中牛源无乳链球菌菌毛岛屿PI-2a的BP基因序列设计1对特异性引物,以无乳链球菌通辽分离株总DNA为模板,PCR扩增BP基因片段并进行序列比对分析. 结果 获得了菌毛岛屿PI-2a的BP基因序列,目的基因为609bp,编码203个氨基酸,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)同源性为100％.BP蛋白二级结构的α螺旋在N端分布较多,β折叠较丰富且分布C端较多,无规则卷曲分布较均匀.BP蛋白的亲水区分布较广,遍布于整个蛋白区,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％,且具有抗原性. 结论 获得了奶牛乳腺炎无乳链球菌通辽分离株菌毛岛屿PI-2a骨架蛋白BP基因序列,该基因序列具有高度保守性,其编码蛋白具有抗原表位,可作为奶牛无乳链球菌重组基因工程疫苗候选亚单位抗原.“,”Objective To clone and sequence a gene that codes for a pilus backbone protein (PI-2a) of Streptococcus agalactiae causing bovine mastitis in the City of Tongliao in Inner Mongolia.Methods The bioinformatic software DNASTAR was used to analyze the sequence of the PI-2a gene of S.agalactiae published in GenBank,the software Primer 5.0 was used to design a pair of specific primers,and total DNA from clinical isolates of S.agalactiae was used as a template to amplify the PI-2a gene fragment.Results The sequence of the PI-2a gene was 609 bp in length and it encoded 203 amino acid residues.The sequence had 100％ similarity to the sequence of a PI-2a gene (EU930008) of S.agalactiae that codes for a pilus backbone protein published in GenBank.a-helices of the secondary structure of the protein were located more at the N-terminus,β-folds were located more at the C-terminus,and random curls were distributed throughout.The backbone protein had hydrophilic regions widely distributed throughout the protein,indicating that the protein is hydrophilic.The protein molecules had a high level of surface accessibility,accounting for as much as 57.0％ of the surface,and the protein was antigenic.Surface-accessible areas of the BP protein were located at amino acids 2-5,15 -20,24-30,33-38,69-78,108-121,123-138,158-164,168-172,and 206-207.Conclusion The sequence of the PI-2a gene was obtained from isolates of S.agalactiae causing bovine mastitis in the Tongliao area.The gene sequence was highly conserved and the protein had epitopes.The protein can be used as a potential subunit antigen with which to genetically engineer a recombinant vaccine against S.agalactiae.