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兴的人类病原体，可感染植入式医疗器械，特别是免疫功能低下患者体内的器械。尽管其作为人类病原体的重要性，S。表皮的特征还不清楚。自S.表皮细胞不产生许多外毒素，我们认为其细胞壁相关的粘附是有效的细菌定植和致病性所必需的。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。S.表皮葡萄球菌表达两种细胞壁锚定蛋白，SdrG和SdrF，它们被预测为粘附素并且与S.金黄色葡萄球菌纤维蛋白原（Fg）结合MSCRA。SdrG与Fg β链的N-末端残基结合，并且是S的附着所必需的。epidermidis到固定化Fg.我们已经解决了SdrG作为脱辅基蛋白和与Fg衍生肽复合的Fg结合区的晶体结构。基于这些结构，我们提出，SdrG改变其构象后，配体结合，在一系列的事件中描述的“码头，锁和闩锁”模型。我们提出，革兰氏阳性MSCRActin，具有SdrG样的预测结构，可以结合线性，肽样配体具有类似的机制。我们已经开始测试“码头，锁和闩锁”模式。我们建议使用几种构象探测技术测试SdrG作为模型分子，随后应用相同的原理和探测其他SdrG样MSCRAbenzene的构象变化。除了结构分析，我们将建立一个小鼠导管感染模型，以探讨特异性Fg结合MSCRA在S.表皮感染奇怪的是，SdrG仅以高亲和力结合人纤维蛋白原。自S.表皮葡萄球菌是唯一的人类病原体，我们将测试SdrG对人纤维蛋白原的特异性是否有助于表皮葡萄球菌。epidermidis人向性。最后，我们将研究另一种SdrG样蛋白SdrF作为S.表皮感染

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.