Meh D A, Siebenlist K R, Galanakis D K, Bergtrom G, Mosesson M W
University of Wisconsin Medical School, Sinai Samaritan Medical Center, Milwaukee, Wisconsin 53233, USA.
Thromb Res. 1995 Jun 15;78(6):531-9. doi: 10.1016/0049-3848(95)00086-7.
In the last stage of fibrinogen synthesis, two Aalpha-Bbeta-gamma half-molecules are disulfide linked in their N-terminal regions to form a dimeric fibrinogen molecule. It is not known whether intracellular hepatocyte assembly of fibrinogen half-molecules occurs randomly or is a directed process. One analysis based on partitioning of coagulable components of fibrinogen from a heterozygous dysfibrinogenemic subject having a mutation at the thrombin cleavage site (Fibrinogen Louisville, Aalpha16 R-->H), suggested that only homodimeric molecules containing two normal fibrinopeptides A (FPA, FPA) or two abnormal fibrinopeptides A (FPA*, FPA*) were present in plasma, implying that fibrinogen dimer assembly is directed. The same type of analyses on Fibrinogen Birmingham (Aalpha16 R-->H) indicated that there were heterodimers as well as homodimers, suggesting that fibrinogen dimer assembly is random. To examine this question more directly, the composition of fibrinogen molecules from seven dysfibrinogenemic families with either R-->C (four) or R-->H (three) Aalpha16 mutations was determined. Following treatment with Atroxin to release normal FPA from fibrinogen, N-terminal disulfide knot ('N-DSK') cleavage fragments were prepared and subsequently separated by SDS-PAGE to resolve 'N-DSK' components with two FPA*'s (N-DSK homodimer), one FPA* (des A N-DSK heterodimer), or no FPA's (des AA N-DSK homodimer). Fibrinogen from subjects whose molecules contained both normal and abnormal Aalpha chains, yielded a heterodimeric des A N-DSK derivative, as well as smaller amounts of homodimeric N-DSK and des AA N-DSK. These results indicate that when both types of Aalpha chain are produced, both Aalpha chain alleles are expressed and the resulting fibrinogen dimers are assembled randomly.
在纤维蛋白原合成的最后阶段，两个Aα-Bβ-γ半分子在其N端区域通过二硫键相连，形成二聚体纤维蛋白原分子。目前尚不清楚纤维蛋白原半分子在肝细胞内的组装是随机发生的还是一个有导向的过程。一项基于对一名在凝血酶切割位点发生突变的杂合性异常纤维蛋白原血症患者（纤维蛋白原路易斯维尔，Aα16 R→H）的可凝固纤维蛋白原成分进行分配的分析表明，血浆中仅存在含有两个正常纤维蛋白肽A（FPA，FPA）或两个异常纤维蛋白肽A（FPA*，FPA*）的同二聚体分子，这意味着纤维蛋白原二聚体的组装是有导向的。对纤维蛋白原伯明翰（Aα16 R→H）进行的同一类型分析表明，存在异二聚体以及同二聚体，这表明纤维蛋白原二聚体的组装是随机的。为了更直接地研究这个问题，测定了来自七个具有R→C（四个）或R→H（三个）Aα16突变的异常纤维蛋白原血症家族的纤维蛋白原分子的组成。在用蛇毒凝血酶从纤维蛋白原中释放出正常FPA后，制备了N端二硫键结（“N-DSK”）切割片段，随后通过SDS-PAGE进行分离，以解析含有两个FPA的“N-DSK”成分（N-DSK同二聚体）、一个FPA（去A N-DSK异二聚体）或不含FPA的成分（去AA N-DSK同二聚体）。来自其分子同时含有正常和异常Aα链的受试者的纤维蛋白原产生了异二聚体去A N-DSK衍生物，以及少量的同二聚体N-DSK和去AA N-DSK。这些结果表明，当产生两种类型的Aα链时，两个Aα链等位基因都会表达，并且产生的纤维蛋白原二聚体是随机组装的。
