CRYSTAL STRUCTURE OF VON WILLEBRAND FACTOR A1 DOMAIN

这项提案的目标是：(一)确定三个 血管性血友病因子(VWF)A1区的空间结构 与肉毒菌素的复合体，这是一种诱导凝集的蛇毒蛋白 通过稳定A1结构域与血小板之间的相互作用 血小板受体糖蛋白Ibalpha；(Ii)测定地壳 三个功能异常的vWF A1结构域突变体的结构 引起IIB型Willebrand病表型；和(Iii)评估 VWF A1结构域是否与第7类A结构域形成络合物 VI型胶原蛋白，并确定复合体的结构。装订 血小板膜糖蛋白(GP)IBpha，是GP IB-IX-V的一个组成部分 受体复合体与vWF A1结构域结合是止血所必需的。 这是唯一能够调节初始粘连的相互作用 在血液流动迅速的血管中，将血小板循环到伤口，如 作为小动脉，允许随后形成止血栓子。 作为了解抗出血的分子基础的第一步 我们已经确定了vWF A1结构域的晶体结构 A1结构域与功能封闭抗体NMC-4形成复合体。这 这项工作导致了对假定的结合表面的识别 血小板受体糖蛋白Ibalpha。这项提议的目标是 获取相关的结构信息以了解vWF的调节 A1结构域与GP Ibalpha结合。我们已经得到了0.2毫米长 VWF A1结构域与调制器之间的络合物的晶体 肉豆素。初步结晶试验的成功证明 该项目的可行性。建筑群的结构将给出 深入了解Botrocetin如何抑制细胞的构象灵活性 A1结构域，从而减缓或阻止与GP IB的解离。 引起IIB型的3个前突变体的晶体结构 威尔布兰德病将揭示这些突变是如何影响构象的 位于它们上方的环路又改变了与GP的交互 伊巴尔法。最后，对二者相互作用的机制进行了探讨。 VWF A1结构域和VI型A7结构域可能揭示了 在血管部位固定vWF的关键步骤的基础 损伤并引发止血或血栓形成。

The objectives of this proposal are: (i) to determine the three dimensional structure of the A1 domain of von Willebrand factor (vWF) in complex with botrocetin, a snake venom protein that induces agglutination on platelets by stabilizing the interaction between the A1 domain and the platelet receptor glycoprotein ibalpha; (ii) to determine the crustal structure of three mutants of the vWF A1 domain with abnormal function causing the type IIB Willebrand disease phenotype; and (iii) to evaluate whether the vWF A1 domains forms a complex with the 7th type A domain of collagen type VI and determine the structure of the complex. The binding of the platelet glycoprotein (GP) IBalpha, a component of the GP IB-IX-V receptor complex, to the vWF A1 domain is essential to arrest bleeding. This is the sole interaction capable of mediating the initial adhesion of circulating platelets to wounds in vessels where blood flow is rapid, such as arterioles, allowing the subsequent development of a hemostatic plug. As a first step to understand the molecular bases of the anti-hemorrhagic function of the vWF A1 domain, we have determined the crystal structure of the A1 domain in complex with the function blocking antibody NMC-4. This work has led to the recognition of a putative binding surface for the platelet receptor glycoprotein Ibalpha. The goal of this proposal is to obtain structural information relevant to understand the regulation of vWF A1 domain binding to GP Ibalpha. We have already obtained 0.2 mm long crystals of the complex between the vWF A1 domain and the modulator botrocetin. Success of the preliminary crystallization trials demonstrates the feasibility of the project. The structure of the complex will give insight into how botrocetin restrains the conformation flexibility of the A1 domain such that dissociation from GP IB is slowed down or blocked. Crystal structures of the three anterior mutants causing type IIB Willebrand disease will reveal how these mutations affect the conformation of the loop situated above them ad in turn change the interactions with GP Ibalpha. Finally, investigation of the mechanism of interaction between vWF A1 domain and collagen type VI A7 domain may reveal the structural bases of a key step necessary for immobilizing vWF at a site of vascular injury and initiating hemostasis or thrombosis.