Examination of the platelet membrane glycoprotein IIb-IIIa complex and its interaction with fibrinogen and other ligands by electron microscopy.
Examination of the platelet membrane glycoprotein IIb-IIIa complex and its interaction with fibrinogen and other ligands by electron microscopy.
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DOI：
10.1016/s0021-9258(18)42050-9
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发表时间：
1992-08
期刊：
影响因子：
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通讯作者：
J. Weisel;C. Nagaswami;G. Vilaire;J. Bennett
中科院分区：
文献类型：
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作者：
J. Weisel;C. Nagaswami;G. Vilaire;J. Bennett
血小板整合素，糖蛋白IIb-IIIa（GPIIb-IIIa），是一种钙依赖性异源二聚体，在血小板活化后结合纤维蛋白原、血管性血友病因子和纤连蛋白。我们研究了GPIIb-IIIa单独和绑定到这些配体的电子显微镜后，用铂/钨旋转阴影。我们发现，如前所述，在洗涤剂和2 mM Ca 2+的存在下，GPIIb-IIIa由一个8 x 12 nm的球状头部和两个从一侧延伸的18 nm柔性尾部组成。我们还发现，在EDTA的存在下，GPIIb-IIIa解离成两个类似的逗号形亚基，每个亚基包含一部分的球状头部和一个单一的尾巴。使用单克隆抗体的GPIIb，GPIIIa，和GPIIb-IIIa异二聚体，我们发现，尾巴包含每个亚基的羧基末端，而结节状的头部是由两个亚基的氨基末端部分。结合到纤维蛋白原的GPIIb-IIIa的电子显微镜显示GPIIb-IIIa的结节状头部与三结节纤维蛋白原分子的远端以及GPIIb-IIIa的尾部相对于纤维蛋白原的长轴以大约98度的角度横向延伸的高度特异性相互作用。当GPIIb-IIIa与单个纤维蛋白原的两端结合时，尾部朝向纤维蛋白原的相对侧，使纤维蛋白原能够桥接两个相邻的血小板。电子显微镜的GPIIb-IIIa绑定到纤连蛋白揭示GPIIb/IIIa结合位点的距离约三分之二的氨基末端的每个末端的纤连蛋白分子，而GPIIb-IIIa被发现绑定到血管性血友病因子原体沿着一个杆状区域附近的中央结节的分子。
The platelet integrin, glycoprotein IIb-IIIa (GPIIb-IIIa), is a calcium-dependent heterodimer that binds fibrinogen, von Willebrand factor, and fibronectin after platelet activation. We examined GPIIb-IIIa alone and bound to these ligands by electron microscopy after rotary shadowing with platinum/tungsten. We found, as observed previously, that in the presence of detergent and 2 mM Ca2+, GPIIb-IIIa consists of an 8 x 12-nm globular head with two 18-nm flexible tails extending from one side. We also found that in the presence of EDTA, GPIIb-IIIa dissociates into two similar comma-shaped subunits, each containing a portion of the globular head and a single tail. Using monoclonal antibodies to GPIIb, GPIIIa, and the GPIIb-IIIa heterodimer, we found that the tails contained the carboxyl termini of each subunit, while the nodular head was composed of amino-terminal segments of both subunits. Electron microscopy of GPIIb-IIIa bound to fibrinogen revealed a highly specific interaction of the nodular head of GPIIb-IIIa with the distal end of the trinodular fibrinogen molecule and with the tails of GPIIb-IIIa extended laterally at an angle of approximately 98 degrees with respect to the long axis of fibrinogen. When a GPIIb-IIIa was bound to each end of a single fibrinogen, the tails were oriented to opposite sides of fibrinogen, enabling fibrinogen to bridge two adjacent platelets. Electron microscopy of GPIIb-IIIa bound to fibronectin revealed GPIIb/IIIa-binding sites approximately two-thirds of the distance from the amino terminus of each end of the fibronectin molecule, while GPIIb-IIIa was found to bind to von Willebrand factor protomers along a rod-like region near the central nodule of the molecule.