Interaction of integrin alphaIIb beta3 with Fibrinogen

The overall shape of integrins is that of a globular 'head' supported by two rod like legs. The ligand-binding pocket is formed by the combination of A-domain or beta-I domain on the beta3 subunit and the putative beta-propeller fold on the alphaIIb subunit in the head regions. The binding of ligand to integrin is also dependent on divalent cations (usually Mn++ or Mg++or Ca++). A conserved motif, the metal ion-dependant adhesion site (MIDAS) is located in the alpha and the beta chains that coordinate the divalent cation at the top of the domain. <br>Active integrin alphaIIb beta3 interacts with a variety of plasma proteins such as fibrinogen, vWF, thrombin, thrombospondin, and fibronectin. The ability of alphaIIbbeta3 to bind fibrinogen plays a crucial role in platelet aggregation and hemostasis. Most of these matrix proteins have integrin binding sites of 3-6 amino acids length, of which the best known are the 'RGD' and 'KGD' motifs. The alpha and beta integrin subunits are both required for ligand binding.

整合素的整体构型呈球形‘头部’，由两根棒状腿支撑。配体结合口袋由β3亚基上的A域或β-I域以及头部区域αIIb亚基上的假定的β-螺旋折叠相结合形成。配体与整合素的结合亦依赖于二价阳离子（通常为Mn++、Mg++或Ca++）。保守的基序，即金属离子依赖性粘附位点（MIDAS），位于α链和β链中，这些链在域顶部协调二价阳离子。活性整合素αIIbβ3与多种血浆蛋白相互作用，如纤维蛋白原、vWF、凝血酶、血栓生成素和纤连蛋白。αIIbbeta3结合纤维蛋白原的能力在血小板聚集和止血过程中发挥着至关重要的作用。大多数这些基质蛋白具有3-6个氨基酸长度的整合素结合位点，其中最著名的是‘RGD’和‘KGD’基序。α和β整合素亚基均为配体结合所必需。