Influence to Biofilm Infection of Surface Protein Mediated by Sortase in Cariogenic Bacteria

为了研究变形链球菌分选酶介导的表面蛋白对生物膜感染的影响，分析了变形链球菌109c的分选酶基因（srtA），构建了突变链球菌109c的srtA缺失突变体。然后通过western blot分析鉴定由该分选酶介导的表面蛋白，并通过srta缺陷突变体s.a mutans 109c鉴定斑块生物膜的形成。克隆srtA基因，确定其完整的核苷酸序列，并根据该核苷酸序列构建srtA缺失突变体S.mutans 109c。该基因序列已存入日本DNA数据库（DDBJ），登录号为AB089932。比较了野生型109c和srtA突变体表面蛋白的定位变化，鉴定了排序酶介导的表面蛋白。结果表明，该分选酶介导至少3种致龋表面蛋白的细胞壁锚定：表面蛋白抗原（PAc）、葡聚糖结合蛋白（GbpC）和葡聚糖酶（Dcx）。研究还表明，在srta缺失突变体中，PAc失去了GbpC和Dex的生理特性，并抑制了斑块生物膜的形成。这些结果表明，在变形链球菌中，srtA基因失活或抑制分选酶对预防菌斑生物膜的形成和随后的龋齿是有用的。

In order to examine influence to biofilm infection of surface protein mediated by the Streptococcus mutans sortase, the sortase gene (srtA) of S.mutans 109c was analyzed and a srtA-deficient mutant of S.mutans 109c was constructed. Surface proteins mediated by the sortase were then identified by western blot analysis and the formation of plaque biofilm by the srtA-deficient mutant of S.mutans 109c. The srtA gene was cloned, the complete nucleotide sequence was determined and then a srtA-deficient mutant of S.mutans 109c was constructed based on the nucleotide sequence. The gene sequence was deposited in the DNA data base of Japan (DDBJ) under the accession number AB089932. Localization change of surface proteins of both wild type 109c and srtA mutant was compared and then the sortase-mediated surface proteins were identified. The result indicated that the sortase mediated the cell-wall anchoring of at least three cariogenic surface proteins: surface protein antigen (PAc), glucan-binding protein (GbpC), dextranase (Dcx). It was also clarified that in the srtA-deficient mutant physiological properties of PAc, GbpC and Dex were lost and the formation of plaque biofilm was inhibited. These results suggested that inactivation of the srtA gene or inhibition of sortase enzyme in S.mutans was useful for the prevention of plaque biofilm formation and subsequent dental caries.