Structure and Function of S. Epidermidis Adhesins

表皮葡萄球菌粘附素的结构和功能

• 批准号: 6813178
• 负责人: MARIA Gabriela BOWDEN
• 金额: $ 18.19万
• 依托单位: TEXAS A&M UNIVERSITY HEALTH SCIENCE CTR
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2006-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6813178
• 关键词: Escherichia coli; Staphylococcus epidermidis; Streptococcus lactis; adhesin; bacteria infection mechanism; bacterial disease; bacterial genetics; conformation; disease /disorder model; fibrinogen; gene expression; host organism interaction; implant; laboratory mouse; ligands; postoperative complications; protein binding; protein purification; protein structure; protein structure function; recombinant proteins

DESCRIPTION (provided by applicant): Staphylococcus epidermidis is an emerging human pathogen that infects implanted medical devices, specially those present in immunocompromised patients. Despite its importance as a human pathogen, the virulence factors of S. epidermidis are not well characterized. Since S. epidermidis does not produce many exotoxins, we propose that its cell wall associated adhesions are essential for effective bacterial colonization and pathogenicity. Therefore, adhesins are attractive targets in the development of novel strategies to prevent and treat infections. S. epidermidis expresses two cell-wall anchored proteins, SdrG and SdrF, that are predicted to be adhesins and are similar to the S. aureus fibrinogen (Fg) binding MSCRAMMs. SdrG binds to the N-terminal residues of the Fg beta chain and is necessary for the attachment of S. epidermidis to immobilized Fg. We have solved the crystal structures of the Fg-binding region of SdrG as an apoprotein and in complex with a Fg-derived peptide. Based on these structures, we propose that SdrG changes its conformation upon ligand binding, in a series of events described in the "dock, lock and latch" model. We propose that Gram-positive MSCRAMMs that have a SdrG-like predicted structure may bind to linear, peptide-like ligands with a similar mechanism. We have begun to test the "dock, lock and latch" model. We propose to use several conformation-probing techniques testing SdrG as a model molecule, and subsequently apply the same principles and probe the conformational changes of other SdrG-like MSCRAMMs. In addition to the structural analysis, we will develop a murine catheter-infection model to explore the role of specific Fg-binding MSCRAMMs in S. epidermidis infections. Curiously, SdrG only binds with high affinity to human fibrinogen. Since S. epidermidis is exclusively a human pathogen, we will test if the SdrG specificity for human fibrinogen contributes to the S. epidermidis human tropism. Finally, we will examine the role of another SdrG-like protein, SdrF, as a virulence factor in S. epidermidis infections.

描述（由申请人提供）：表皮葡萄球菌是一种新兴的人类病原体，可感染植入的医疗装置，尤其是在免疫功能低下的患者中的病原体。尽管它是人类病原体的重要性，但表皮链球菌的毒力因子并未得到很好的特征。由于表皮链球菌不会产生许多外毒素，因此我们建议其细胞壁相关的粘连对于有效的细菌定植和致病性至关重要。因此，粘合剂是开发预防和治疗感染的新型策略的吸引力目标。表皮链球菌表达两个细胞壁锚定的蛋白SDRG和SDRF，这些蛋白被预测为粘附蛋白，与金黄色葡萄球菌纤维蛋白原（FG）结合MSCramms相似。 SDRG与FGβ链的N末端残基结合，对于将表皮链球菌的附着在固定的FG上是必不可少的。我们已经解决了SDRG的FG结合区域的晶体结构，并与FG衍生的肽相结合。基于这些结构，我们建议SDRG在“码头，锁定和闩锁”模型中描述的一系列事件中改变了对配体结合的构象。我们提出，具有类似SDRG的预测结构的革兰氏阳性MSCRAMMS可能与具有相似机制的线性，肽样的配体结合。我们已经开始测试“码头，锁定和闩锁”型号。我们建议将测试SDRG测试的几种构象探针作为模型分子，然后应用相同的原理并探测其他类似SDRG的MSCramms的构象变化。除结构分析外，我们还将开发一个鼠导管感染模型，以探讨特定的FG结合MSCRAMMS在表皮链球菌感染中的作用。奇怪的是，SDRG仅与人类纤维蛋白原具有高亲和力结合。由于表皮链球菌仅是人类病原体，因此我们将测试人类纤维蛋白原的SDRG特异性是否有助于表皮链球菌人类的特性。最后，我们将研究另一种SDRG样蛋白SDRF作为表皮链球菌感染中的毒力因子的作用。