STRUCTURE OF ORAL BACTERIAL ADHESINS

描述（由申请人提供）：口腔中居住着500多种革兰氏阳性和革兰氏阴性细菌，这些细菌存在于称为生物膜的复杂生态系统中。生物膜的形成是由口腔链球菌附着在覆盖口腔表面的获得性唾液膜上开始的。随着生物膜的发展和成熟，条件变得有利于晚期细菌定植者的附着，这些细菌定植者与牙周疾病相关。细菌粘附到获得性唾液膜或宿主受体是生物膜形成、细菌定植和感染的关键步骤。细菌粘附是由菌毛和非菌毛粘附素介导的，它们是展示在细菌表面的含有受体结合结构域的蛋白质附属物。菌毛粘附素形成由单个亚基或多个亚基的多个拷贝组成的长丝状结构。S.副血吸虫由Fap 1（菌毛相关蛋白1）的多个亚基组成，这对生物膜的形成至关重要。最近在其他链球菌家族成员中发现了Fap-1同源物。非菌毛粘附素形成由单个亚基或少量相同亚基组成的较短结构，所述亚基特异性折叠以暴露远端的受体结合结构域。A.伴放线菌使用特异性非菌毛粘附素粘附并侵入上皮细胞以及与细胞外基质蛋白相互作用。EmaA（Extracellular matrix protein adhesin-A）是一种新发现的非菌毛粘附素。放线菌共生菌参与结合宿主组织中的胶原蛋白和微管蛋白。EmaA是一种多聚体自转运蛋白，其通过3或4个亚基的寡聚化在细菌细胞表面上形成结构（总分子量为600-800 kDa）。这种粘附素和/或粘附素/受体复合物的结构信息是未知的。由于抗生素耐药生物体数量的增加，关于粘附素/受体相互作用的详细3D结构信息对于下一代治疗剂的开发极其重要。然而，到目前为止，关于口腔细菌的结构信息还很缺乏。在此应用中，我们建议确定早期细菌定植者（Fap-1）和晚期定植者（EmaA）的粘附素和粘附素/受体复合物的3D结构，这对于深入了解致病过程的不同阶段至关重要。我们将使用电子显微镜和图像处理的新技术进行这些研究。我们的工作将提供这些粘附素和相应的粘附素/受体复合物的第一个三维结构数据。 项目叙述：人类口腔中有500多种细菌，它们是导致口腔和严重的口腔外系统性疾病的原因。由细胞表面粘附素介导的细菌粘附是生物膜形成、定植和感染的关键步骤。我们将确定粘附素和粘附素/受体复合物的3D结构，这对于深入了解致病过程的不同阶段至关重要。

DESCRIPTION (provided by applicant): The oral cavity is inhabited by more than 500 species of Gram-positive and Gram-negative bacteria, which exist in a complex ecosystem referred to as a biofilm. Biofilm formation is initiated by the attachment of oral streptococci to the acquired salivary pellicle coating the surfaces of the oral cavity. As the biofilm develops and matures, conditions become propitious for the attachment of the late bacterial colonizers, which are associated with periodontal disease to the existing biofilm. Bacterial adhesion to the acquired salivary pellicle or to host receptors is a crucial step for biofilm formation, bacterial colonization and infection. Bacterial adhesion is mediated by fimbrial and non-fimbrial adhesins, which are proteinaceous appendages displayed on the surface of bacteria containing the receptor binding domains. Fimbrial adhesins form long filamentous structures composed of multiple copies of either a single subunit or multiple subunits. The long-fimbriae of S. parasanguis are composed of multiple subunits of Fap1 (fimbriae-associated protein 1), which are crucial for biofilm formation. Fap-1 homologues have recently been found in other streptococcal family members. Non-fimbrial adhesins form shorter structures comprised of either a single subunit or a small number of identical subunits specifically folding to expose the receptor binding domain at the distal-end. A. actinomycetemcomitans uses specific non-fimbrial adhesins to adhere to and invade into epithelial cells as well as interacting with extracellular matrix proteins. EmaA (Extracellular matrix protein adhesin-A) is a newly discovered non-fimbrial adhesin of A. actinomycetemcomitans involved in binding to collagen and tubulin in the host tissue. EmaA is a multimeric autotransporter protein, which forms structures on the bacterial cell surface by oligomerization of either 3 or 4 subunits (total molecular mass of 600-800 kDa). Structural information on this adhesin and/or the adhesin/receptor complexes is unknown. Detailed 3D structural information on adhesin/receptor interactions is extremely important for the development of next generation therapeutics due to the increase number of antibiotic resistant organisms. To date, however, there is a paucity of structural information regarding oral bacteria. In this application, we propose to determine the 3D structure of the adhesins and adhesin/receptor complexes of both an early bacterial colonizer (Fap-1) and a late colonizer (EmaA) essential to gain insights into the different stages of the pathogenic process. We will carry out these studies using novel techniques of electron microscopy and image processing. Our work will provide the first 3D structural data for these adhesins and the respective adhesin/receptor complexes. PROJECT NARRATIVE: The human oral cavity is inhabited by more than 500 species of bacteria, which are responsible for causing oral and serious extra-oral systemic diseases. Bacterial adhesion, mediated by adhesins on the cell surface, is a crucial step for biofilm formation, colonization, and infection. We will determine the 3D structure of the adhesins and adhesin/receptor complexes, which is essential to gain insights into the different stages of the pathogenic process.