Mechanisms for ligand binding by serine-rich adhesins of Gram-positive pathogens

革兰氏阳性病原体富含丝氨酸的粘附素的配体结合机制

• 批准号: 8788229
• 负责人: T M Iverson
• 金额: $ 75.48万
• 依托单位: NORTHERN CALIFORNIA INSTITUTE/RES/EDU
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8788229
• 关键词: Address; Affinity; Animal Disease Models; Animal Model; Architecture; Attenuated; Bacteria; Bacterial Adhesins; Binding; Blood; Blood Circulation; Blood Platelets; Carbohydrates; Cell Wall; Dependence; Development; Disease; Disease Progression; Disease model; Endocarditis; Endocardium; Family; Fibrin; Glycoproteins; Goals; Gram-Positive Bacteria; Heart Valves; Homologous Gene; Human; In Vitro; Infection; Infective endocarditis; Injury; Lead; Lectin; Lesion; Ligand Binding; Ligands; Mediating; Membrane; Microbe; Modeling; Molecular; Morbidity - disease rate; Mutagenesis; Mutation; Organism; Pathogenesis; Process; Property; Pulsatile Flow; Relative (related person); Research; Role; Serine; Site; Site-Directed Mutagenesis; Streptococcus; Streptococcus Viridans Group; Streptococcus gordonii; Structure; Surface; System; Tissues; Translating; Trisaccharides; Tropism; Variant; Viral Tumor Antigens; Virulence; Work; antigen binding; antimicrobial; base; fluid flow; insight; microbial; mortality; novel; pathogen; public health relevance; receptor; shear stress; sialic acid binding Ig-like lectin

DESCRIPTION (provided by applicant): The serine-rich repeat (SRR) glycoproteins are a large family of adhesins found in many Gram-positive bacteria. These surface components are important virulence determinants for a broad range of human infections. GspB is an SRR adhesin of Streptococcus gordonii that mediates binding to human platelets through its interaction with the trisaccharide sialyl-T antigen (sTa) on the platelet receptor GPIb. This binding appears to be important for the pathogenesis of infective endocarditis, since mutagenesis of the GspB binding region results in decreased platelet binding in vitro, and reduced virulence in an animal model of this disease. Three properties of GspB binding may be highly important for the targeting of streptococci to the endocardium: affinity, selectivity, and fow enhancement. First, the binding of GspB to its platelet receptor is a high affinity interaction (KD 2.4 x 10-8 M). Second, GspB has a very selective binding spectrum, with sTa being its principal ligand. Third, GspB-mediated binding by bacteria to sTa is enhanced by levels of fluidic shear flow similar to those within the endovascular system. In combination, these three binding properties may target blood-borne streptococci to platelets immobilized at sites of endocardial injury (thereby initiating infection). GspB-mediated binding may also contribute to the subsequent formation of macroscopic endocardial lesions (vegetations) containing bacteria and platelets. This project seeks to define the molecular basis for GspB binding affinity, selectivity, and flow enhancement, and the relative importance of these properties for virulence. Aim 1 will examine how the molecular architecture of the GspB binding domain confers affinity and selectivity. We will determine the structure of the GspB binding region cocrystallized with sTa and related compounds, select key domains and residues for targeted mutagenesis, and examine the impact of these mutations on binding affinity and selectivity. Two GspB homologs (Hsa and SrpA) that differ in their binding properties will also be evaluated. Aim 2 will determine the structural features of GspB that contribute to flow-enhanced binding, and whether binding occurs via the formation of catch bonds. We will specifically examine the contribution of the serine-rich repeat domains of GspB in flow-enhanced binding. Aim 3 will assess the impact of ligand affinity, selectivity and flow-enhanced binding on the pathogenesis of infective endocarditis. Isogenic variants of S. gordonii strain M99 that differ in their ligand binding properties will be compared for relative virulence, using a well-established co-infection model of this disease. This project will provide significant insights into the structural basis for carbohydrate binding by this novel group of bacterial adhesins, as well as the mechanisms for streptococcal binding to human platelets. In addition, these studies could provide a basis for novel therapies for infective endocarditis that target SRR glycoprotein binding.

描述（由申请方提供）：富含丝氨酸重复序列（SRR）糖蛋白是在许多革兰氏阳性菌中发现的粘附素大家族。这些表面组分是广泛的人类感染的重要毒力决定因素。GspB是戈登链球菌的SRR粘附素，其通过与血小板受体GPIb上的三糖唾液酸-T抗原（sTa）相互作用介导与人血小板的结合。这种结合似乎对感染性心内膜炎的发病机制很重要，因为GspB结合区的突变会导致体外血小板结合减少，并降低该疾病动物模型的毒力。GspB结合的三个特性对于链球菌靶向内分泌物可能非常重要：亲和力、选择性和流动增强。首先，GspB与其血小板受体的结合是高亲和力相互作用（KD 2.4 x 10-8 M）。其次，GspB具有非常选择性的结合谱，sTa是其主要配体。第三，GspB介导的细菌与sTa的结合通过类似于血管内系统内的流体剪切流的水平而增强。结合起来，这三种结合特性可以将血源性链球菌靶向固定在内皮损伤部位的血小板（从而引发感染）。GspB介导的结合也可能有助于随后形成含有细菌和血小板的肉眼可见的内皮损伤（赘生物）。该项目旨在确定GspB结合亲和力，选择性， 以及这些特性对毒力的相对重要性。目的1将研究GspB结合结构域的分子结构如何赋予亲和力和选择性。我们将确定与sTa和相关化合物共结晶的GspB结合区的结构，选择关键结构域和残基进行靶向诱变，并检查这些突变对结合亲和力和选择性的影响。还将评价结合特性不同的两种GspB同系物（Hsa和GspA）。目标2将决定 有助于流动增强结合的GspB的结构特征，以及结合是否通过形成捕获键发生。我们将专门研究GspB富含丝氨酸的重复结构域在流动增强结合中的贡献。目的3将评估配体亲和力、选择性和流动增强结合对感染性心内膜炎发病机制的影响。S.将使用该疾病的良好建立的共感染模型，比较配体结合特性不同的戈登氏菌菌株M99的相对毒力。该项目将提供重要的见解，碳水化合物结合的结构基础，这一新的细菌粘附素，以及链球菌结合人类血小板的机制。此外，这些研究可以为针对SRR糖蛋白结合的感染性心内膜炎的新型疗法提供基础。