UNIQUE ASPECTS OF C1-- INHIBITOR STRUCTURE / FUNCTION

C1-抑制剂是丝氨酸蛋白酶抑制剂家族的血浆蛋白酶抑制剂。 C1抑制剂的生理靶点是补体成分C1的活化C1 r和C1 s亚基以及接触系统的酶。 缺乏C1抑制剂，无论是遗传性或获得性，可导致血管性水肿，一个潜在的致命条件。 尽管C1抑制剂与其他丝氨酸蛋白酶抑制剂有许多共同之处，但它也有一些独特的特性，这些特性尚未被详细研究。 首先，与其他丝氨酸蛋白酶抑制剂相比，它缓慢地抑制蛋白酶。 其结构原因尚不清楚。 最初将确认，作为C1的一部分，C1 s抑制在其生理形式下缓慢发生。 然后将通过使用C1-抑制剂突变体和C1-抑制剂-α 1-蛋白酶抑制剂嵌合体来研究抑制活性的结构基础。 C1-inhibitor具有高度糖基化的110个氨基酸的氨基端结构域，与其他丝氨酸蛋白酶抑制剂没有同源性。 该区域的功能将进行调查，特别是测试的想法，它是必不可少的快速抑制和随后的解离C1。 为了测试该重组C1-抑制剂变体，将制备缺乏部分或全部氨基末端的变体。 还将单个半胱氨酸引入氨基末端结构域，其可以用荧光团标记以评估该区域与C1和靶蛋白酶的相互作用。 这些主题将在以下三个目的进行研究：目的1）确定C1抑制剂在分离时和在C1复合物中的抑制率;目的2）确定C1抑制剂抑制活性的结构基础;目的3）确定C1抑制剂氨基末端结构域的功能。 这些研究将提供关于C1-抑制剂的结构-功能关系的重要信息，其对蛋白质的体内功能、蛋白质的治疗用途以及由天然存在的功能障碍变体引起的缺陷状态具有影响。

C1-inhibitor is a plasma proteinase inhibitor of the serpin family. The physiological targets for C1-inhibitor are the activated C1r and C1s subunits of complement component C1, and enzymes of the contact system. Deficiency of C1-inhibitor, either hereditary or acquired can cause angioedema, a potentially fatal condition. Although C1-inhibitor has much in common with other serpins, it has some unique characteristics which have not been investigated in detail. Firstly, it inhibits proteinases slowly compared to other serpins. The structural reasons for this are not known. Initially it will be confirmed that C1s inhibition occurs slowly when in its physiological form, as part of C1. Then the structural basis for the inhibitory activity will be studied by use of C1-inhibitor mutants and C1-inhibitor- alpha1-proteinase inhibitor chimeras. C1-inhibitor has a highly glycosylated 110 residue amino-terminal domain which has no homology with other serpins. The function of this region will be investigated, in particular testing the idea that it is essential for rapid inhibition and subsequent dissociation of C1. To test this recombinant C1-inhibitor variants lacking part or all of the amino-terminal will be made. Also single cysteines will be introduced into the amino-terminal domain which can be labeled with fluorophore to assess the interaction of this region with C1 and the target proteinases. These topics will be studied in the following three aims: Aim 1) To determine the rate of C1s inhibition when isolated and when in the C1 complex; Aim 2) To determine the structural basis for the inhibitory activity of C1-inhibitor; and Aim 3) To determine the function of the amino-terminal domain of C1-inhibitor. These studies will provide important information regarding structure-function relationships in C1-inhibitor, which has implications for the in vivo function of the protein, the therapeutic use of the protein, and for the deficiency states caused by naturally occurring dysfunctional variants.