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出现的人类病原体，它会感染植入的医疗设备，特别是那些存在于免疫功能低下患者体内的医疗设备。尽管表皮葡萄球菌作为人类病原体很重要，但其毒力因子尚未得到很好的表征。由于表皮葡萄球菌不产生许多外毒素，我们认为其细胞壁相关的粘附对于有效的细菌定植和致病性至关重要。因此，粘附素是开发预防和治疗感染的新策略的有吸引力的靶标。表皮葡萄球菌表达两种细胞壁锚定蛋白 SdrG 和 SdrF，预计它们是粘附素，并且与金黄色葡萄球菌纤维蛋白原 (Fg) 结合 MSCRAMM 相似。 SdrG 与 Fg β 链的 N 端残基结合，对于表皮葡萄球菌与固定化 Fg 的附着是必需的。我们已经解析了 SdrG 的 Fg 结合区作为脱辅基蛋白并与 Fg 衍生肽复合的晶体结构。基于这些结构，我们提出SdrG在配体结合后在“对接、锁定和闩锁”模型中描述的一系列事件中改变其构象。我们提出，具有 SdrG 样预测结构的革兰氏阳性 MSCRAMM 可能以类似的机制与线性肽样配体结合。我们已经开始测试“对接、锁定和闩锁”模式。我们建议使用几种构象探测技术来测试 SdrG 作为模型分子，随后应用相同的原理并探测其他类似 SdrG MSCRAMM 的构象变化。除了结构分析之外，我们还将开发小鼠导管感染模型，以探索特异性 Fg 结合 MSCRAMM 在表皮葡萄球菌感染中的作用。奇怪的是，SdrG 仅以高亲和力与人纤维蛋白原结合。由于表皮葡萄球菌是一种人类病原体，我们将测试 SdrG 对人类纤维蛋白原的特异性是否有助于表皮葡萄球菌的人类趋向性。最后，我们将研究另一种 SdrG 样蛋白 SdrF 作为表皮葡萄球菌感染毒力因子的作用。