摘要目的 研究副血链球菌(Streptococcus parasanguis)fap1-orf4基因座位编码的葡糖基转移酶(GTF)和开放阅读框架(ORF)4是否参与菌毛相关蛋白1(Fap1)的糖基化与成熟以及两种蛋白质之间的相互作用.方法 采用基因置换技术构建副血链球菌gtf和orf4突变株,并利用互补分析和Western blot检测副血链球菌Fap1的表达水平,用以评价GTF和ORF4在Fap1的糖基化和成熟的作用,另外采用酵母双杂交技术、GST pulldown技术检测GTF和ORF4两种蛋白质的相互作用.结果 (1)副血链球菌gtf和orf4的突变株呈现相同表型,成熟的相对分子质量(M)约220×103的Fap1被高相对分子质量不成熟的Fap1(Mr约360×103)所取代.互补分析显示pVPT-GFP-gtf和pVPT-GFP-orf4能使突变株恢复表达成熟的Fap1;(2)酵母双杂交技术的划线试验显示共转化子AH109/pAD-gtf+pBD-orf4和AH109/pAD-00f4+pBD-gtf均能在营养缺陷的选择性培养基SD-LTHA上生长,而共转化子AH109/pAD+pBD-orf4、AH109/pAD+pBD-gtf、AH109/pBD+pAD-orf4、AH109/pBD+pAD-gtf不能在营养缺陷的培养基上生长;酵母双杂交技术的X-α-ga1试验显示共转化子AH109/pAD+pBD-orf4和AH109/pAD-orf4+pBD-gtf呈现蓝色.(3)GST pull down技术进一步证实GTF和ORF4两种蛋白质之间存在直接的相互作用.结论 副血链球菌fap1-orf4基因座位编码的GTF和ORF4之间存在相互作用,GTF和ORF4组成复合物是Fap1成熟与糖基化所必需的.

abstractsObjective To investigate whether glucosyltransfernse(GTF) and open reading frame 4 (ORF4) coded by fap1-orf4 gene locus of Streptococcus parasanguis was involved in the regulation of Fap1 glycosylation, and mature and to determine whether there was interaction between GTF and ORF4. Methods A gene replacement strategy was adapted to construct gtf and orf4 allele replace mutant of S. Parasanguis. Complementation assay and Western blot were used to test fap1 expression levels. Yeast two-hybrid analysis and GST pull down assays were adapted to determine the interaction between GTF and ORF4. Results (1) Compared with wild S. Parasanguis, mature Fapl (Mr about 220×103) disappeared and were substituted with high molecular weight Fapl (Mr about 360×103) in gtf or orf4 alleie replace mutants of S. Parasan-guis. Complementation assay showed that pVPT-GFP-gtf and pVPT-GFP-orf4 restored mature fap1 expression in gtf or orf4 alleie replace mutants, respectively. (2) With Yeast two-hybrid analysis, the eotransformants, AH109/pAD-Gtf+pBD-orf4 and AHlOg/pAD-orf4+pBD-gtf growed on SD-LTHA selective ngar plate after streaked, reversely, the eotransformants, AH109/pAD+pBD-orf4,AH109/pAD+pBD-gtf、AH109/pBD+ pAD-orf4、AH109/pBD+pAD-gtf did not grow on SD-LTHA selective agar plate, furthermore, the cotrans-formants, AH109/pAD+pBD-orf4 and AH109/pAD-orf4+pBD-gtfshowed blue during X-α-gal assay. (3) GST pull down assay confirmed the direct interaction between GTF and ORF4. Conclusion There is inter-action between GTF and ORF4 coded byfapl-orf4 gene locus of S. Parasangnis and the formation of the GTF and ORF4 complex was required for the glycosylation and mature of Fapl in S. Parasanguis.