Characterization of Vitamin K Epoxide Reductase

描述（由申请人提供）：该项目的长期目标不仅是了解维生素K环氧化物还原酶（VKOR）的结构和功能，而且还了解整个维生素K周期。维生素k依赖性羧化是蛋白质翻译后必需的修饰，在多种生理功能中起重要作用，包括凝血和骨代谢。VKOR是华法林的靶标，华法林是最广泛用于血栓栓塞性疾病的抗凝剂。虽然估计华法林每次诱发出血发作可预防20次中风，但由于担心出血，华法林仍未得到充分利用。希望这项资助的研究将导致抗血栓治疗的改进，从而避免华法林治疗的一些问题。具体而言，我们建议在拨款期内完成以下工作：(1)利用标准纯化和酶分析方法、RNAi技术和修饰表达克隆，我们将研究维生素K循环，以鉴定生产维生素K对苯二酚所需的维生素K环氧化还原酶（VKOR）以外的组分；(2)利用电子晶体学、生化和分子生物学技术，对VKOR的三维结构进行研究。(3)使用体内和体外方法研究VKOR所需的结构特征。

DESCRIPTION (provided by applicant): The long-term objective of this project is to understand, not only the structure and function of the vitamin K epoxide reductase (VKOR), but also the vitamin K cycle as a whole. Vitamin K-dependent carboxylation is an essential post-translational modification for proteins important in several physiologic functions, including blood coagulation and bone metabolism. VKOR is the target of warfarin, the most widely prescribed anti-coagulant for thromboembolic disorders. Although estimated to prevent twenty strokes per induced bleeding episode, warfarin is still under-utilized because of fear of bleeding. It is hoped that research funded by this grant will lead to improved anti- thrombotic therapies that will avoid some of the problems related to warfarin treatment. Specifically, we propose to accomplish the following during the tenure of this grant: (1) using standard purification and enzyme assay methods, RNAi technologies, and modified expression cloning, we will investigate the vitamin K cycle to identify components other than the vitamin K epoxide reductase (VKOR) necessary for the production of vitamin K hydroquinone, (2) employing electron crystallography, biochemical and molecular biological techniques, conduct studies to elucidate the three- dimensional structure of VKOR, and (3) using both in vivo and in vitro methods investigate the structural characteristics necessary for VKOR. PUBLIC HEALTH RELEVANCE: In addition to development of new ways of controlling thromboses, knowledge gained from our research on the vitamin K cycle should give insight into the vitamin's apparently major role in bone formation. While the contribution to bone metabolism is clear, it is still controversial whether vitamin K is useful in treating or slowing progression of bone density loss in osteoporosis. Another developing area relevant to public health is the role of coagulation/thrombosis in cancer, and in turn whether vitamin K and its antagonists have a place in cancer treatment.