Evidence for the "Dock, Lock, and Latch" ligand binding mechanism of the staphylococcal microbial surface component recognizing adhesive matrix molecules (MSCRAMM) SdrG
Evidence for the "Dock, Lock, and Latch" ligand binding mechanism of the staphylococcal microbial surface component recognizing adhesive matrix molecules (MSCRAMM) SdrG
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DOI：
10.1074/jbc.m706252200
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发表时间：
2008-01-04
影响因子：
4.8
通讯作者：
Hook, Magnus
中科院分区：
文献类型：
--
作者：
Bowden, M. Gabriela;Heuck, Alejandro P.;Hook, Magnus
表皮葡萄球菌是一种机会致病菌，也是引起异物感染的主要原因。色葡萄表皮纤维蛋白原（Fg）结合粘附素SdrG对于该病原体与Fg包被的材料的附着是必要的且足够的。主要基于SdrG作为脱辅基蛋白和与Fg样肽复合的配体结合结构域的结构分析，我们提出SdrG遵循“对接、锁定和闩锁”机制与Fg结合。这种结合机制涉及配体在两个SdrG亚结构域之间形成的口袋中的对接，随后是一个亚结构域的C-末端延伸的移动以覆盖配体并插入和补充相邻亚结构域中的β-折叠。这些提出的事件导致MSCRAMM-配体复合物的极大稳定的闭合构象。在这份报告中，我们描述了一个生化分析的建议构象变化，SdrG后，结合到其配体。我们已经将二硫键引入SdrG中以稳定MSCRAMM的apo形式的开放和闭合形式。我们表明，稳定的封闭形式不结合的配体和结合可以恢复还原剂如二硫苏糖醇的存在下。我们还使用福斯特共振能量转移动态显示构象变化的SdrG结合其配体。最后，我们已经使用等温量热法来确定，配体和蛋白质之间的疏水相互作用是负责重定向触发β链互补事件所需的第二亚结构域的C-末端延伸。
Staphylococcus epidermidis is an opportunistic pathogen and a major cause of foreign body infections. The S. epidermidis fibrinogen (Fg)-binding adhesin SdrG is necessary and sufficient for the attachment of this pathogen to Fg-coated materials. Based largely on structural analyses of the ligand binding domain of SdrG as an apo-protein and in complex with a Fg-like peptide, we proposed that SdrG follows a "dock, lock, and latch" mechanism to bind to Fg. This binding mechanism involves the docking of the ligand in a pocket formed between two SdrG subdomains followed by the movement of a C-terminal extension of one subdomain to cover the ligand and to insert and complement a beta-sheet in a neighboring subdomain. These proposed events result in a greatly stabilized closed conformation of the MSCRAMM-ligand complex. In this report, we describe a biochemical analysis of the proposed conformational changes that SdrG undergoes upon binding to its ligand. We have introduced disulfide bonds into SdrG to stabilize the open and closed forms of the apo-form of the MSCRAMM. We show that the stabilized closed form does not bind to the ligand and that binding can be restored in the presence of reducing agents such as dithiothreitol. We have also used Forster resonance energy transfer to dynamically show the conformational changes of SdrG upon binding to its ligand. Finally, we have used isothermic calorimetry to determine that hydrophobic interactions between the ligand and the protein are responsible for re-directing the C-terminal extension of the second subdomain required for triggering the beta-strand complementation event.