GLUCAN BINDING PROTEINS OF ORAL STREPTOCOCCI

变形链球菌（Streptococcus mutans）是龋病的病原体，具有多种葡聚糖结合蛋白（GBP），这些蛋白有助于其粘附和定殖牙齿表面的能力。 酶（GBP）是催化葡聚糖合成的葡糖基转移酶（GTF）。非酶（GBP）被认为有助于粘附，聚集和斑块的连贯性，但它们的作用没有得到很好的记录。因此，尽管S.尽管GBP与变形链球菌发病机制密切相关，但GBP多样性的确切贡献和必要性尚未确定。 也许因此，缺乏专门干扰这些S的临床措施。变形菌毒力因子已经发现，失活f gbpA（编码非酶GBP的基因）导致大鼠模型中毒力的变化和变异生物体的积累，所述变异生物体已经经历了相邻gtfB和gtfC基因之间的重组以形成杂合gtfBC。 相对于野生型，GTF重组体产生减少量的葡聚糖。 有人提出，gbpA的失活导致斑块结构的变化，这反过来又带来了选择性保留的GTF重组体。 以下具体目的是在检查个体GBP对斑块基质形成的贡献的背景下检验该假设。 1)确定GbpA突变体中GTF重组体的体内积累是由于重组频率增加还是由于选择力，并研究重组的分子机制。 2)基因工程改造一种沙门氏菌。通过将gbpA的多个拷贝引入到生物体中而过表达GbpA的变异株。 3)在大鼠模型中测试基因工程GbpA++和GbpA+过表达，以检查对GTF重组体定殖、龋齿发展和积累的影响。 4)制备含有S.变形蛋白GTF-I、GTF-SI和GTF-S，并测定它们对葡聚糖和变形蛋白的亲和力。 将结果与GbpA的结果进行比较。 5)通过检查S的插入突变体，确定gbpA上游的DNA是否编码影响葡糖基转移酶表达或分布的产物。变异株LT 11具有增加的细胞表面GTF水平。 总之，这些研究代表了一种新的方法，其靶向GbpA作为降低葡糖基转移酶活性的机制，从而降低S.变异人

Streptococcus mutans, the etiologic agent of dental caries, possesses several glucan binding proteins (GBPs) which contribute to its ability to adhere to, and colonize, tooth surfaces. The enzymatic (GBPs) are the glucosyltransferases (GTFs) which catalyze the synthesis of the glucans. The nonenzymatic (GBPs) are thought to contribute to adherence, aggregation, and the coherence of plaque but their roles are not as well documented. Thus, despite the general understanding of S. mutans pathogenesis, the precise contributions and necessity of the multiplicity of GBPs have yet to be determined. Perhaps as a consequence, there are a lack of clinical measures to specifically interfere with these S. mutans virulence factors. It has been found that the inactivation f gbpA, a gene encoding a nonenzymatic GBP, results in a change in virulence in a rat model and the accumulation of variant organisms which have undergone a recombination between the contiguous gtfB and gtfC genes to form a hybrid gtfBC. The GTF recombinants produce decreased amounts of glucan relative to the wild type. It is proposed that the inactivation of gbpA leads to a change in plaque structure and this in turn brings about a selective retention of GTF recombinants. The following specific aims test this hypothesis within the context of examining the contribution of individual GBPs to the formation of the plaque matrix. 1) Determine whether the in vivo accumulation of GTF recombinants among the GbpA mutants is due to an increased frequency of recombination or is due to selection forces, and investigate the molecular mechanism of he recombination. 2) Genetically engineer a strain of S. mutans that overexpresses GbpA by introducing multiple copies of gbpA into the organism. 3) Test the genetically engineered GbpA++ and GbpA+++ overexpresser in a rat model to examine the effects on colonization, caries development, and accumulation of GTF recombinants. 4) Make fusion proteins containing the glucan binding domains of the S. mutans GTF-I, GTF-SI, and GTF-S and determine their affinities for dextran and mutan. Compare the results with those obtained for GbpA. 5) Determine if the DNA upstream of gbpA encodes products that affect the expression or distribution of the glucosyltransferases by examining an insertional mutant of S. mutans LT11 that possesses increased levels of cell surface GTFs. Overall these studies represent a novel approach which targets GbpA as a mechanism for reducing glucosyltransferase activity and thereby the virulence of S. mutans.