Structure and Function of S. Epidermidis Adhesins

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，可感染植入医疗器械，特别是存在于免疫功能低下患者中的植入医疗器械。尽管表皮葡萄球菌作为一种重要的人类病原体，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是必不可少的。因此，黏附素在预防和治疗感染的新策略的发展中是有吸引力的目标。表皮葡萄球菌表达两种细胞壁锚定蛋白，SdrG和SdrF，这两种蛋白被预测为黏附素，与金黄色葡萄球菌纤维蛋白原（Fg）结合的msmrms相似。SdrG与Fg β链的n端残基结合，是表皮葡萄球菌附着于固定化Fg的必要条件。我们已经解决了SdrG作为载脂蛋白和与fg衍生肽复合物的fg结合区域的晶体结构。基于这些结构，我们提出SdrG在配体结合时改变其构象，在“dock, lock and latch”模型中描述了一系列事件。我们提出，具有类似sdg预测结构的革兰氏阳性mrmrms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“dock, lock and latch”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来探测其他类似SdrG的msram的构象变化。除了结构分析外，我们还将建立小鼠导管感染模型，以探索特异性fg结合mscrms在表皮葡萄球菌感染中的作用。奇怪的是，SdrG只与人纤维蛋白原高亲和力结合。由于表皮葡萄球菌是一种专门的人类病原体，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倾向。最后，我们将研究另一种sdrg样蛋白SdrF在表皮葡萄球菌感染中作为毒力因子的作用。

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.