Crystal structures of the membrane-binding C2 domain of human coagulation factor V

Rapid and controlled clot formation is achieved through sequential activation of circulating serine proteinase precursors on phosphatidylserine-rich procoagulant membranes of activated platelets and endothelial cells. The homologous complexes Xase and prothrombinase, each consisting of an active proteinase and a non-enzymatic cofactor, perform critical steps within this coagulation cascade. The activated cofactors VIIIa and Va, highly specific for their cognate proteinases, are each derived from precursors with the same A1-A2-B-A3-C1-C2 architecture. Membrane binding is mediated by the C2 domains of both cofactors. Here we report two crystal structures of the C2 domain of human factor Va. The conserved beta-barrel framework provides a scaffold for three protruding loops, one of which adopts markedly different conformations in the two crystal forms. We propose a mechanism of calcium-independent, stereospecific binding of factors Va and VIIIa to phospholipid membranes, on the basis of (1) immersion of hydrophobic residues at the apices of these loops in the apolar membrane core; (2) specific interactions with phosphatidylserine head groups in the groove enclosed by these loops; and (3) favourable electrostatic contacts of basic side chains with negatively charged membrane phosphate groups.     

脑梗死患者血浆中凝血因子Ⅶ测定及临床意义

目的 :探讨脑梗死患者血浆中凝血因子Ⅶ的变化及临床意义。方法 :FⅦAg测定采用ELISA法 ;FⅦa 测定采用重组可溶性因子法 ;FⅦc 测定采用一阶段凝固法。结果 :35例脑梗死FⅦAg为 (75± 15) % ,FⅦa为 (2 .8± 0 .9)ng/mL ,FⅦc 为 (97± 2 4 ) %。与健康老人组比较FⅦa、FⅦc 水平增高 ,表明患者存在高凝状态。结论 :FⅦ是脑梗死的危险因素 ,其中FⅦa 水平升高更为有意义。     

冠心病合并2型糖尿病女性患者冠状动脉造影特点分析

目的分析冠心病合并2型糖尿病女性患者冠状动脉造影特点及临床危险因素,探讨糖尿病对冠状动脉病变的作用机制。方法将2005年11月～2008年11月在我院经冠状动脉造影确诊为冠心病的女性患者168例,按有无2型糖尿病（DM）分为糖尿病组（DM组）和非糖尿病组（nonDM组）,对其冠状动脉造影资料、危险因素进行分析研究。结果冠状动脉病变特点：冠状动脉受累血管及严重程度DM组比nonDM组显著高（P〈0．01）。临床危险因素：收缩压、舒张压、空腹血糖（FBG）、餐后2h血糖（2hBG）、糖化血红蛋白（GHbA。C）、总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白胆固醇（LDL—C）、载脂蛋白B（ApoB）DM组比nonDM组高（P〈0．05）,且与冠状动脉狭窄程度呈正相关（P〈0．05）。高密度脂蛋白胆固醇（HDL—C）、载脂蛋白A1（Apo A1）DM组比nonDM组显著低（P〈0．01）,且与冠状动脉狭窄程度呈负相关（P〈0．05）。两组年龄、体重指数（BMI）差异无显著性（P〉0．05）。结论冠心病合并2型糖尿病女性患者冠状动脉病变程度重,除糖尿病外,常与高血压、高血脂等危险因素同时存在。     

凝血因子IX的体外检测方法研究

凝血因子ＩＸ的检测是血友病Ｂ基因治疗研究中的重要工作，在实验室原有基础上，发现和完善了凝血因子ＩＸ在蛋白质水平上的检测系统，为基因治疗血友病Ｂ提供了更为直观可靠的依据。首先，建立了以鼠抗人ＦＩＸ单克隆抗体Ａ－７为一抗的检测活性ＦＩＸ蛋白量的ＥＬＩＳＡ法，为检测活性ＦＩＸ提供了快速简便的方法。其次，实现了用Ｗｅｓｔｅｒｎｂｌｏｔ法检测转染细胞培养液上清中ＦＩＸ，确证了体外培养的转有人ＦＩＸｃＤＮＡ细     

Human chromosomal mapping of genes for insulin-like growth factors I and II and epidermal growth factor

Many of the actions previously attributed to pituitary-derived growth hormone are mediated by polypeptide growth factors. These include the insulin-like growth factors I and II (IGF-I and IGF-II), which are members of the insulin family of proteins. We report here the chromosomal mapping of the human genes for IGF-I and IGF-II. IGF-II maps to the short arm of chromosome 11, which also contains the gene for insulin and the proto-oncogene c-Ha-ras1 (ref. 9). IGF-I maps to chromosome 12, which is evolutionarily related to chromosome 11 and carries the gene for the proto-oncogene c-Ki-ras2 (refs 10,44). We have also localized the human gene for an unrelated polypeptide hormone, epidermal growth factor, to chromosome 4q, in the same region as another specialized growth factor, T-cell growth factor. We speculate that these map assignments reflect the existence of gene families involved in growth control.     

Polymorphisms in genes involved in folate metabolism as maternal risk factors for Down syndrome in China

Objective： To explore the relationship between genetic polymorphisms in methylenetetrahydrofolate reductase （MTHFR）, methionine synthase reductase （MTRR）, the central enzymes in folate metabolism that affects DNA methylation and synthesis, and the risk of Down syndrome in China. Methods： Genomic DNA was isolated from the peripheral lymphocytes of 64 mothers of children with Down syndrome and 70 age matched control subjects. Polymerase chain reaction and restriction fragment length polymorphism were used to examine the polymorphisms of MTHFR 677C→T, MTRR 66A→G and the relationship between these genotypes and the risk of Down syndrome was analyzed. Results： The results show that the MTHFR 677C→T polymorphism is more prevalent among mothers of children with Down syndrome than among control mothers, with an odds ratio of 3.78 （95% confidence interval （CI）, 1.78-8.47）. In addition, the homozygous MTRR 66A→G polymorphism was independently associated with a 5.2-fold increase in estimated risk （95% CI, 1.90-14.22）. The combined presence of both polymorphisms was associated with a greater risk of Down syndrome than the presence of either alone, with an odds ratio of 6.0 （95% CI, 2.058-17.496）. The two polymorphisms appear to act without a multiplicative interaction. Conclusion： MTHFR and MTRR gene mutation alleles are related to Down syndrome, and CT, TT and GG gene mutation types increase the risk of Down syndrome.     

Identification of the V factor needed for synthesis of the iron-molybdenum cofactor of nitrogenase as homocitrate

Nitrogenase catalyses the ATP-dependent reduction of N2 to NH3, and is composed of two proteins, dinitrogenase (MoFe protein or component I) and dinitrogenase reductase (Fe protein or component II). Dinitrogenase contains a unique prosthetic group (iron-molybdenum cofactor, FeMoco) comprised of Fe, Mo and S, which has been proposed as the site of N2 reduction. Biochemical and genetic studies of Nif- (nitrogen fixation) mutants of Klebsiella pneumoniae which are defective in nitrogen fixation, have shown that the nifB, nifQ, nifN, nifE and nifV genes are required for the biosynthesis of FeMo-co. Recently, a system for in vitro synthesis of FeMoco was described. The assay requires at least the nifB, nifN and nifE gene products, and a low-molecular-weight factor (V factor) produced in the presence of the nifV gene product. We have used this system to study FeMoco biosynthesis. We report here the isolation of V factor and identify it as homocitric acid ([R]2-hydroxy-1,2,4-butanetricarboxylic acid).