Molecular Assembly on the Cell Surface of Actinomyces

描述（由申请人提供）：细菌病原体的成功感染需要附着在宿主组织上并定植。表面决定簇（菌毛和非菌毛表面蛋白）对于所有细菌病原体中的这些过程至关重要，因为它们提供与决定细菌宿主范围和感染部位的组织因子的特异性受体-配体相互作用。在第一批定殖人类牙齿的细菌中，放线菌和口腔链球菌可能成为与携带菌和牙周病病因相关的其他物种定殖的基础。放线菌的菌毛和非菌毛表面成分可能在发病机制中发挥重要作用，因为它们能够与宿主细胞相互作用并激活宿主细胞。由于缺乏有关放线菌细胞表面组成的详细分子信息，并且缺乏简单的遗传系统来研究不同成分的作用，这些相互作用的潜在机制仍然不清楚。使用生物信息学方法，我们鉴定了内氏放线菌 MG-1 未完成基因组中的两个菌毛基因簇。通过生化和电子显微镜分析，我们证明每个基因簇编码一个独特的菌毛结构，该结构由菌毛轴蛋白和主要位于尖端区域的小亚基组成。它们组装成菌毛结构需要基因簇中发现的特定转肽酶、分选酶。此外，我们还鉴定了许多假定的表面蛋白，其中大多数根据序列特征预测参与细胞与细胞的相互作用。我们假设放线菌与宿主细胞受体和感染伙伴的相互作用可能涉及各种菌毛和非菌毛因素。因此，该提案的长期目标是描述放线菌表面分子的组装机制并检查它们在细菌感染中的作用。结合电子显微镜、质谱和分子生物学，我们的目标是确定放线菌菌毛的分子结构及其蛋白质交联的化学性质。将采用遗传和生化实验来定义菌毛组装的酶、底物和产物。重要的是，我们将确定菌毛和非菌毛因素是否有助于放线菌与宿主细胞和其他病因成分的相互作用。产生的结果应该为未来研究这些生物体在其生态位中的生物过程提供充足、强大的实验系统。我们的建议旨在表征口腔细菌放线菌的表面结构，这些细菌可能在牙菌斑形成中发挥重要作用。产生的结果将允许开发阻止表面蛋白或菌毛组装的抑制剂，这可能被证明是预防携带病和牙周病的有用策略。

DESCRIPTION (provided by applicant): Successful infections by bacterial pathogens require attachment to and colonization of host tissues. Surface determinants (fimbrial and non-fimbrial surface proteins) are essential for these processes in all bacterial pathogens as they provide specific receptor-ligand interactions with tissue factors that determine both bacterial host range and sites of infection. Among the first bacteria to colonize human teeth, actinomyces together with oral streptococci may serve as a foundation for the colonization of other species that are associated with the etiology of carries and periodontal diseases. Fimbriae and non-fimbrial surface components of Actinomyces may have important roles in pathogenesis owing to their ability to interact with and activate host cells. The underlying mechanisms of these interactions remain obscure due to the absence of detailed molecular information on the composition of the Actinomyces cell surface and the lack of a facile genetic system to investigate the role of different components. Using a bioinformatics approach, we have identified the two fimbrial gene clusters in the unfinished genome of Actinomyces naeslundii MG-1. By biochemical and electron microscopy analysis, we have demonstrated that each gene cluster encodes a distinct fimbrial structure comprised of a fimbrial shaft protein and a minor subunit located largely at the tip region. Their assembly into fimbrial structures requires a specific transpeptidase, sortase, found in the gene cluster. Furthermore, we also have identified many putative surface proteins, a majority of which are predicted to participate in cell-cell interactions based on sequence features. We hypothesize that interactions of Actinomyces with host cell receptors and infectious partners may involve various fimbrial and non- fimbrial factors. Thus, the long term goal of this proposal is to delineate the mechanisms of assembly of the surface molecules of Actinomyces and to examine their role in bacterial infection. Using a combination of electron microscopy, mass spectrometry and molecular biology, we aim to determine the molecular architecture of Actinomyces fimbriae and the chemical nature of their protein cross-linkages. Genetic and biochemical experiments will be employed to define the enzymes, substrates and products of fimbrial assembly. Importantly, we will determine whether fimbrial and non-fimbrial factors contribute to the interactions of Actinomyces with host cells and other etiological components. The results generated should provide ample, powerful experimental systems for future studies on the biological processes of these organisms in their ecological niche. Our proposal aims to characterize surface structures of oral bacteria Actinomyces that may play an important role in plaque formation. The generated results will permit the development of inhibitors which block the assembly of surface proteins or fimbriae that may prove a useful strategy for preventing carries and periodontal diseases.