THE FUNCTIONS OF PROTEIN C

活化的蛋白C是一种有效的抗凝血剂，它还可以刺激 纤溶作用。凝血酶结合时蛋白C迅速激活 与一种特定的内皮细胞表面受体血栓调节蛋白结合。 血栓调节蛋白加速凝血酶催化的蛋白C活化 钙依赖反应。钙离子在蛋白C激活中的作用 将与蛋白C和蛋白C进行运动学分析 作为底物的GLA结构域已经被移除。初步数据 提示蛋白C上存在高亲和力的钙结合部位 不同于依赖于GLA的钙结合部位。这个网站将是 通过平衡透析法和本征荧光变化法进行研究。 血栓调节蛋白通常是一种膜蛋白。凝血酶催化的蛋白质 C的激活是通过血栓调节蛋白重组为 膜。重组凝血酶调节蛋白的条件 将对膜进行测定，并研究脂类的特异性。 将重新评估重组系统的动力学，以确定 脂质增强的性质。血栓调节蛋白在体内的浓度 内皮细胞表面尚不清楚。一种抗人免疫球蛋白单抗 将产生血栓调节蛋白并用于确定 血栓调节蛋白分子/内皮细胞。从动力学研究来看，它将是 可以确定内皮细胞是否提供独特的属性 它不能被合成系统复制。人类血栓调节蛋白将 像以前对兔子所做的那样分离和鉴定 血栓调节蛋白。人蛋白C、人血栓调节蛋白的动力学研究 人体内皮细胞将被执行。活化蛋白C 介导的抗凝血活性还没有完全确定。虽然 活化蛋白C抑制因子Va失活速度太慢 以说明抗凝剂的作用。S蛋白刺激Va因子 失活，但体外刺激的程度不能解释 等离子体刺激。低水平活化蛋白C的影响 血浆凝血酶原和凝血因子V激活的时程研究 在纯化的系统中将被监测以确定单独的蛋白C 或与S蛋白一起影响凝血酶原激活发生前的滞后 或者是否影响凝血酶原的速度和/或程度 消费。血小板支持活化蛋白C的能力 抗凝血活性也将被调查。

Activated protein C is a potent anticoagulant which also stimulates fibrinolysis. Activation of protein C occurs rapidly when thrombin binds to a specific endothelial cell surface receptor, thrombomodulin. Thrombomodulin accelerates thrombin catalyzed protein C activation in a Ca++ dependent reaction. The role of Ca++ in the activation of protein C will be analyzed kinetically with both protein C and protein C from which the Gla domain has been removed as the substrate. Preliminary data suggests the presence of a high affinity Ca++ binding site on protein C distinct from the Gla dependent Ca++ binding sites. This site will be studied by equilibrium dialysis and by intrinsic fluorescence changes. Thrombomodulin is normally a membrane protein. Thrombin catalyzed protein C activation is accelerated by reconstitution of thrombomodulin into membranes. The conditions for reconstitution of thrombomodulin into membranes will be determined and the specificity of the lipids studied. The kinetics of the reconstituted system will be re-evaluated to determine the nature of the lipid enhancement. The thrombomodulin concentration on the endothelial cell surface is not known. A monoclonal antibody to thrombomodulin will be produced and used to determine the number of thrombomodulin molecules/endothelial cell. From kinetic studies it will be possible to determine if the endothelial cell provides unique properties which cannot be duplicated by synthetic systems. Human thrombomodulin will be isolated and characterized as done previously for rabbit thrombomodulin. Kinetic studies on human protein C, human thrombomodulin and human endothelial cells will be performed. Activated protein C mediated anticoagulant activity is not completely characterized. Although activated protein C inhibits factor Va the rate of inactivation is too slow to account for the anticoagulant effect. Protein S stimulates factor Va inactivation, but the extent of stimulation in vitro does not account for the plasma stimulation. The influence of low levels of activated protein C on the time course of both prothrombin and factor V activation in plasma and in purified systems will be monitored to determine if protein C alone or with protein S influences the lag before prothrombin activation occurs or whether it influences the rate and/or extent of prothrombin consumption. The ability of platelets to support activated protein C anticoagulant activity will also be investigated.