INTERACTION OF STREPTOCOCCAL SURFACE LECTINS WITH SALIVARY AGGLUTININS

唾液凝集素（Salivary agglutinin，SAG）是一种粘蛋白样糖蛋白， 在调节口腔组织的链球菌定殖中起重要作用。 固定在组织表面的SAG可促进链球菌粘附 而可溶性SAG聚集链球菌， 从口腔中分离出来 色葡萄sanguis和S.变形 SAG的受体是钙依赖性凝集素， 相当大的序列和结构相似性。 然而，碳水化合物 这些蛋白质的结合特异性是物种特异性的。 我们 对定义碳水化合物结合的分子基础感兴趣 特异性和钙在这些凝集素相互作用中的作用 关于SAG 在本申请中，我们提出识别 参与糖识别和钙离子转运的特异性凝集素结构域 约束力 钙的凝集素活性的依赖性将是 通过监测凝集素的碳水化合物结合能力进行研究 其中钙结合位点已被位点特异性 诱变 我们还将评估其结构和功能 SAG受体与其他口腔链球菌的相似性。 最后 克隆的凝集素将用作亲和树脂以鉴定和 表征SAG的特定碳水化合物结构， 被S. sanguis和S.变形菌凝集素 了解 结构变化如何影响一组相关 蛋白质对于治疗方法的合理设计显然很重要， 潜在的疫苗候选人 这似乎特别适用于口腔 链球菌，其中病原体和 非致病性生物体由高度相似的蛋白质介导。

Salivary agglutinin (SAG) is a mucin-like glycoprotein which plays an important role in modulating streptococcal colonization of oral tissues. SAG immobilized on tissue surfaces may promote streptococcal adherence while soluble SAG aggregates streptococci and may function in clearance of these organisms from the mouth. The S. sanguis and S. mutans receptors for SAG are calcium dependent lectins which exhibit considerable sequence and structural similarity. However, carbohydrate binding specificity of these proteins is species specific. We are interested in defining the molecular basis of carbohydrate binding specificity and the role of calcium in the interaction of these lectins with SAG. In the present application, we propose to identify the specific lectin domains involved in sugar recognition and calcium binding. the dependency of lectin activity of calcium will be investigated by monitoring the carbohydrate binding capacity of lectins in which calcium binding sites have been inactivated by site specific mutagenesis. We will also evaluate the structural and functional similarities of SAG receptors from other oral streptococci. Finally, the cloned lectins will be utilized as affinity resins to identify and characterize the specific carbohydrate structures of SAG which are recognized by the S. sanguis and S. mutans lectins. An understanding of how structural variation influences function within a group of related proteins is clearly important for the rational design of therapeutics and potential vaccine candidates. This appears especially pertinent for oral streptococci, where bacterial/host interactions of both pathogenic and non-pathogenic organisms are mediated by highly similar proteins.