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ANTICOAGULANT PROTEIN COMPLEX STRUCTURE AND FUNCTION

抗凝蛋白复合物的结构和功能

基本信息

批准号：
6638726
负责人：
TIMOTHY A. MATHER
金额：
$ 24万
依托单位：
OKLAHOMA MEDICAL RESEARCH FOUNDATION
依托单位国家：
美国
项目类别：
财政年份：
2001
资助国家：
美国
起止时间：
2001-02-05 至 2005-07-31
项目状态：
已结题

项目摘要

DESCRIPTION (Applicant's Description Verbatim): The enzymatic phase of the anticoagulation system functions by the proteolytic digestion and down-regulation of the procoagulant cofactors factors VIIla and Va by the enzyme activated protain C(APC). Hereditary defects in this system lead to a congenital predisposition to venous thrombosis. The pathway is initiated when thrombin (T) binds to thrombomodulin (TM) on the endothelium and undergoes a cofactor dependent allosteric conformational change. In the TM bound conformation, thrombin loses its procoagulant activity, and gains an alternative substrate selectivity. The T-TM complex now recognizes the zymogen protein C as its substrate and very efficiently activates it. Thus, the major procoagulant enzyme takes on an anticoagulant activity and catalyzes its own down-regulation as a result of this cofactor induced allosteric modulation. The structural nature of this transition is completely unknown. If we could understand this specificity switch on a structural basis, we might begin to design therapeutic agents which could bind to thrombin and shift it from a procoagulant towards an anticoagulant activity. Based on the results of APC infusion in septic shock, this therapeutic approach leads to a wider window of efficacy without increased bleeding. We propose to study the structure and function of the T-TM complex with X-ray crystallography to understand the structural origin of thrombin's anticoagulant activity. We have grown diffracting crystals of one form of this complex and are currently solving its structure. We plan to build on this initial success to solve the structures of related complexes, each designed to show an additional aspect of this activity, and to apply our findings towards explaining the ability of some small molecules and thrombin point mutations to achieve partial anti-coagulant activity. Ultimately we will undertake structure based drug design to improve these partial effects.

描述(申请者逐字描述)：酶促阶段抗凝系统通过蛋白水解性消化和促凝血辅因子Vi1a和Va的下调作用酶激活蛋白C(APC)。这一系统中的遗传缺陷导致了先天易患静脉血栓形成。该途径在以下情况下启动凝血酶(T)与内皮上的血栓调节蛋白(TM)结合并经历辅因子依赖的变构构象变化。在TM范围内构象，凝血酶失去其促凝血活性，并获得替代底物选择性。T-TM复合体现在识别酶原蛋白C作为它的底物，非常有效地激活它。因此，少校促凝血酶具有抗凝血活性，并催化自身这种辅因子的下调导致变构调节。这个这一过渡的结构性质完全未知。如果我们能够在结构的基础上理解这种特定的转换，我们可能会开始设计可以与凝血酶结合并转移它的治疗剂从促凝剂转变为抗凝血剂。基于以下结果：感染性休克的APC输注，这一治疗方法导致了更宽的窗口在不增加出血的情况下提高疗效。我们建议研究它的结构和用X射线结晶学研究T-TM复合体的功能凝血酶抗凝血活性的结构来源。我们已经成长了这种络合物的一种形式的衍射晶体，目前正在解决其结构。我们计划在这一初步成功的基础上解决相关的综合体，每个都旨在展示这一活动的另一个方面，并应用我们的发现来解释一些小的分子和凝血酶点突变实现部分抗凝活动。最终，我们将进行基于结构的药物设计以改进这些部分效应。