COORDINATE FUNCTION OF ENZYME COMPLEXES IN HEMOSTASIS

参与血液凝固的蛋白质必须组装， 迅速发挥作用，以防止创伤后出血。 的特征 有助于效率的凝结是酶反应的定位 到细胞膜。 在止血过程中两种膜结合酶 复合物依次起作用以产生凝血酶。 两种膜 复合物需要蛋白质快速、高亲和力的膜结合 辅因子定位相应的酶并启动酶功能。 酶复合物在功能上是相关的，因为酶复合物的产物是 第一种复合物是tenase，它是一种酶，然后与辅因子组装 形成第二种复合物凝血酶原酶。 虽然功能的 分离的酶复合物已经被表征为没有机理 这两种酶复合物如何协同发挥作用的信息。 具体地，任一酶复合物对酶的功能的影响都是通过酶复合物的作用来确定的。 另一种是未知的，Xa因子从tenase转移的机制 与凝血酶原酶复合物的复合物是未知的。 最近，我展示了 这两种辅因子蛋白，因子VIII和因子V， 彼此结合到膜表面。 因为因子V和因子 VIII各自增强另一个的膜结合，它们很可能结合 彼此之间 因子VIII与因子V的结合可能是物理上的， 将两种酶复合物彼此相邻的机制， 为了有效地转移因子Xa以形成tenase酶复合物， 以形成凝血酶原酶复合物。拟议 实验将研究因子VIII和因子V 快速结合到膜上，结合蛋白在膜上的移动性 膜的 此外，他们将表征因子VIII的结合 并确定结合的酶促结果 互动

The proteins which participate in blood coagulation must assemble and function rapidly in order to prevent bleeding after trauma. A feature of coagulation which aids in efficiency is localization of enzymatic reactions to membranes. In the hemostatic process two membrane-bound enzyme complexes function sequentially to produce thrombin. Both membrane complexes require the rapid, high affinity membrane binding of a protein cofactor to localize the respective enzyme and initiate enzymatic function. The enzyme complexes are functionally related because the product of the first complex, tenase, is an enzyme which then assembles with a cofactor to form the second complex, prothrombinase. Although function of the isolated enzyme complexes has been characterized there is no mechanistic information to explain how the two enzyme complexes function coordinately. Specifically, the effect of either enzyme complex upon the function of the other is unknown and the mechanism of transfer of factor Xa from the tenase complex to the prothrombinase complex is unknown. Recently, I have shown that the two cofactor proteins, factor VIII and factor V, enhance the binding of one another to a membrane surface. Because factor V and factor VIII each enhance membrane binding of the other it is likely that they bind to each other. Binding of factor VIII to factor V may be the physical mechanism which places the two enzyme complexes adjacent to one another in order to efficiently transfer factor Xa to form the tenase enzyme complex to factor Va to form a prothrombinase enzyme complex. The proposed experiments will examine the mechanism whereby factor VIII and factor V bind rapidly to a membrane and the mobility of the bound proteins upon the membrane. In addition they will characterize the binding of factor VIII to factor V and define the enzymatic consequences of the binding interaction.