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首页> 外文期刊>Infection and immunity >Analysis of the virulence of Streptococcus mutans serotype c gtfA mutants in the rat model system.
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Analysis of the virulence of Streptococcus mutans serotype c gtfA mutants in the rat model system.

机译：大鼠模型系统中变形链球菌血清型c gtfA突变体的毒力分析。

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The Streptococcus mutans serotype c gtfA gene encodes a 55-kilodalton protein which catalyzes the synthesis of a small glucan (1.5 kilodaltons) from sucrose (J.P. Robeson, R.G. Barletta, and R. Curtiss III, J. Bacteriol. 153:211-221, 1983). To investigate the role of the GtfA enzyme in virulence, we constructed S. mutans gtfA mutants from three cariogenic serotype c strains. A plasmid that carried an erythromycin resistance determinant and an internal fragment of the gtfA gene but that was unable to replicate in streptococci was used to transform S. mutans. The erythromycin-resistant transformants carried a partial duplication of the internal gtfA fragment, because of the integration of plasmid sequences within the S. mutans gtfA gene, which also resulted in the inactivation of the gtfA gene. This was verified by Southern DNA hybridization analysis and Western blot studies of cellular protein extracts of the mutant strains with GtfA antiserum. Mutants were fully virulent in both germfree and conventional rats. These results do not rule out the involvement of the GtfA protein in virulence. Pucci and Macrina (M.J. Pucci and F.L. Macrina, Infect. Immun. 54:77-84, 1986) have suggested that the GtfA enzyme synthesizes a primer for water-insoluble glucans. Another S. mutans protein, presumably a glucosyltransferase, may have a similar function and, thus, may obscure the relevance of the GtfA enzyme in pathogenesis.
机译：变形链球菌血清型c gtfA基因编码一个55公斤的蛋白质，该蛋白质催化从蔗糖（JP Robeson，RG Barletta和R. Curtiss III，J. Bacteriol。153：211-221， 1983）。为了研究GtfA酶在毒力中的作用，我们从三种致龋性血清型c菌株构建了变形链球菌gtfA突变体。携带红霉素抗性决定簇和gtfA基因内部片段但不能在链球菌中复制的质粒被用于转化变形链球菌。由于变形链球菌gtfA基因内质粒序列的整合，红霉素抗性转化体携带了内部gtfA片段的部分重复，这也导致gtfA基因失活。通过Southern DNA杂交分析和具有GtfA抗血清的突变株细胞蛋白提取物的Western印迹研究证实了这一点。突变株在无菌和常规大鼠中均具有完全毒性。这些结果不排除GtfA蛋白参与毒力。 Pucci和Macrina（M.J.Pucci和F.L.Macrina，Infect.Immun.54：77-84，1986）表明，GtfA酶合成了水不溶性葡聚糖的引物。另一种变形链球菌蛋白，可能是葡糖基转移酶，可能具有相似的功能，因此可能会掩盖GtfA酶在发病机理中的相关性。

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