蛋白C（PC）缺陷症是亚洲人静脉血栓形成最重要危险因素之一。PC由r-羧基谷氨酸区（Gla）和表皮生长因子样区（EGF1）等五个结构区构成。EGF1区的突变与血栓发生相关,但其致病机制均不明确。EGF1区与Ca2+结合是维持EGF1及Gla区正常功能的保证，但PC的EGF1与Ca2+的结合方式尚不明确，有报道EGF1区的Asp71是Ca2+结合的关键位点。本项目组在两例Ⅱ型PC缺陷症伴血栓患者中分别发现了两种新突变Ile73Asn和Gly74Ser，均位于EGF1且与Asp71相邻。据此我们推测突变可能通过相邻结构的改变影响Ca2+的结合及EGF1功能。拟通过体外表达突变及野生型PC探讨：突变对EGF1区与Ca2+的结合的影响；突变对EGF1区与辅因子蛋白S结合的影响（体外和动物体内）；突变是否间接影响Gla区与内皮细胞PC受体及磷脂结合。从而阐明两种PC突变导致抗凝功能异常分子机制。

Inherited Protein C (PC) deficiency resulted from PC mutations is one of the most important risk factors for venous thromboembolism in Asian population. It mainly consists of five domains, including γ-carboxyglutamic acid domain (Gla) and epidermal growth factor-like domains (EGF1) and et al. Mutations located on the EGF1 domain are associated with thromboembolism, but the pathogenetic mechanism is unclear. Normal binding between calcium and EGF1 is the prerequisite for maintaining the function of EGF1 and Gla domains. The ligation between calcium and consensus residues on EGF1 of PC is not yet elucidated，and it is reported that the key residue of calcium binding to EGF1 is the aspartic acid 71 (Asp71). We have identified two novel mutations Ile73Asn and Gly74Ser, located on EGF1, which are close to Asp71 in two unrelated patients with Based on current findings, we speculate that the two mutations might impair the calcium affinity for EGF1 by altering adjacent structure, thus influencing the normal function of EGF1. In this study, we will express and purify these two variants and wild-type recombinant PC to investigate: 1. the effects of the two mutant PC on the affinity for calcium; 2. the effects of the two mutant PC on the interaction between protein S (PS) and EGF1 by in vitro and in vivo detection; 3. the indirect impairment of the two mutant PC to the binding of Gla and endothelial protein C receptor (EPCR) or Gla and phospholipids. Therefore, the molecular pathogenesis of anticoagulation defects caused by two mutations will be explored through current project.