Zn2+ Mediates High Affinity Binding of Heparin to the αC Domain of Fibrinogen
Zn2+ Mediates High Affinity Binding of Heparin to the αC Domain of Fibrinogen
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DOI：
10.1074/jbc.m113.469916
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发表时间：
2013-10-11
影响因子：
4.8
通讯作者：
Weitz, Jeffrey I.
中科院分区：
文献类型：
--
作者：
Fredenburgh, James C.;Leslie, Beverly A.;Weitz, Jeffrey I.
肝素与血浆蛋白的非特异性结合会减少可用于结合抗凝血酶的肝素量，从而损害其抗凝活性。此外，肝素与纤维蛋白的相互作用促进三元肝素-凝血酶-纤维蛋白复合物的形成，该复合物保护纤维蛋白结合的凝血酶免受肝素-抗凝血酶复合物的抑制。先前的研究表明，肝素与纤维蛋白原的 E 结构域结合。目前的研究检查了 Zn2+ 在这种相互作用中的作用，因为 Zn2+ 由血小板局部释放，肝素和纤维蛋白原都与阳离子结合，从而更好地防止抗凝血酶的抑制。通过色谱、荧光和表面等离子共振测定，Zn2+ 促进肝素与纤维蛋白原结合。与完整的纤维蛋白原相比，肝素与片段X（纤维蛋白原的可凝性纤溶酶降解产物）的结合减少。针对被纤溶酶去除的纤维蛋白原 α C 结构域的一部分的单克隆抗体减弱了肝素与纤维蛋白原的结合，并且该区域的肽类似物以 Zn2+ 依赖性方式结合肝素。这些结果表明纤维蛋白原的 α C 结构域含有 Zn2+ 依赖性肝素结合位点。因此，当 Zn2+ 存在时，纤维蛋白原会更大程度地损害抗凝血酶对肝素催化的 Xa 因子的抑制作用。这些结果揭示了Zn2+增强纤维蛋白原损害肝素抗凝活性的能力的机制。
The nonspecific binding of heparin to plasma proteins compromises its anticoagulant activity by reducing the amount of heparin available to bind antithrombin. In addition, interaction of heparin with fibrin promotes formation of a ternary heparin-thrombin-fibrin complex that protects fibrin-bound thrombin from inhibition by the heparin-antithrombin complex. Previous studies have shown that heparin binds the E domain of fibrinogen. The current investigation examines the role of Zn2+ in this interaction because Zn2+ is released locally by platelets and both heparin and fibrinogen bind the cation, resulting in greater protection from inhibition by antithrombin. Zn2+ promotes heparin binding to fibrinogen, as determined by chromatography, fluorescence, and surface plasmon resonance. Compared with intact fibrinogen, there is reduced heparin binding to fragment X, a clottable plasmin degradation product of fibrinogen. A monoclonal antibody directed against a portion of the fibrinogen alpha C domain removed by plasmin attenuates binding of heparin to fibrinogen and a peptide analog of this region binds heparin in a Zn2+-dependent fashion. These results indicate that the alpha C domain of fibrinogen harbors a Zn2+-dependent heparin binding site. As a consequence, heparin-catalyzed inhibition of factor Xa by antithrombin is compromised by fibrinogen to a greater extent when Zn2+ is present. These results reveal the mechanism by which Zn2+ augments the capacity of fibrinogen to impair the anticoagulant activity of heparin.