Crystal structure of the A3 domain of human von Willebrand factor: implications for collagen binding
Crystal structure of the A3 domain of human von Willebrand factor: implications for collagen binding
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DOI：
10.1016/s0969-2126(97)00266-9
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发表时间：
1997-09-15
期刊：
影响因子：
5.7
通讯作者：
Gros, P
中科院分区：
文献类型：
--
作者：
Huizinga, EG;vanderPlas, RM;Gros, P
背景：受损血管的出血可通过血小板栓的形成而停止。多聚体血浆糖蛋白，血管性血友病因子（vWF），通过在高剪切应力条件下将血小板锚定到受损的血管壁，在此过程中发挥重要作用。该因子通过与受损血管的胶原蛋白和血小板膜上的糖蛋白Ib结合来介导血小板粘附。vWF的A3结构域允许其结合存在于受损血管壁的血管周围结缔组织中的I型和III型胶原。为了深入了解vWF与胶原蛋白结合的机制，我们测定了人vWF A3结构域的晶体结构。结果：用多波长反常色散法在1.8埃分辨率下测定了人vWF A3结构域（残基920-1111）的晶体结构，显示出共同的二核苷酸结合折叠。推定的A3结构域的胶原结合位点是相当平滑的，并且显示出显著高浓度的带负电荷的残基。该区域包含含有基序DXSXS的潜在金属结合位点，其是整合素CR 3和LFA-1的同源I型结构域中的配体相互作用所需的。虽然vWF A3有相当大的序列和结构相似性，CR 3和LFA-1在这个区域，A3的一个环采用的构象是不兼容的离子binding.Conclusions：A3结构域的结构表明，粘附到胶原蛋白主要是通过A3上的带负电荷的残基和胶原蛋白上的带正电荷的残基之间的相互作用实现的。没有明显的结合沟排除了A3和胶原蛋白之间的大的货车范德华表面相互作用，并且与单个A3结构域对胶原蛋白的低亲和力和多聚体vWF与胶原蛋白紧密结合的需要一致。在将晶体浸泡在MgCl 2中时不存在结合的金属离子，并且vWF A3对于金属结合的构象不相容性与A3中不存在金属离子结合的功能作用一致，这与同源整合素I型结构域的配体结合所需的金属离子活化形成对比。
Background: Bleeding from a damaged blood vessel is stopped by the formation of a platelet plug. The multimeric plasma glycoprotein, von Willebrand factor (vWF), plays an essential role in this process by anchoring blood platelets to the damaged vessel wall under conditions of high shear stress. This factor mediates platelet adhesion by binding both to collagen of the damaged blood vessel and to glycoprotein Ib on the platelet membrane. The A3 domain of vWF allows it to bind to collagen types I and III present in the perivascular connective tissue of the damaged vessel wail. To gain insight into the mechanism of collagen binding by vWF, we have determined the crystal structure of the human vWF A3 domain.Results: The crystal structure of the 20 kDa A3 domain of human VWF (residues 920-1111), determined by the method of multiwavelength anomalous dispersion at 1.8 Angstrom resolution, exhibits a common dinucleotide-binding fold. The putative collagen-binding site of the A3 domain is rather smooth and shows a markedly high concentration of negatively charged residues. This region encompasses a potential metal-binding site containing the motif DXSXS, which is required for ligand interaction in the homologous I-type domains of integrins CR3 and LFA-1. Although vWF A3 has considerable sequence and structural similarity with CR3 and LFA-1 in this region, one loop of A3 adopts a conformation which is incompatible with ion binding.Conclusions: The structure of the A3 domain suggests that adhesion to collagen is primarily achieved through interactions between negatively charged residues on A3 and positively charged residues on collagen. The absence of a pronounced binding groove precludes a large van der Waals surface interaction between A3 and collagen and is consistent with the low affinity for collagen of a single A3 domain and the requirement for multimeric vWF for tight association with collagen. The absence of bound metal ions upon soaking the crystal in MgCl2 and vWF A3's conformational incompatibility for metal binding is consistent with the absence of a functional role for metal ion binding in A3, which contrasts the metal ion activation required for ligand binding by the homologous integrin I type domains.