Mosher D F
J Biol Chem. 1975 Aug 25;250(16):6614-21.
Cold-insoluble globulin (CI globulin) was purified from human plasma and identified on the basis of its sedimentation coefficient, electrophoretic mobility, and concentration in normal plasma. CI globulin was distinguished from antihemophilic factor (AHF) by amino acid analysis, position of elution from 4% agarose, and electrophoretic migration in polyacrylamide gels in the presence of sodium dodecyl sulfate without prior reduction. CI globulin and AHF could not be distinguished by polyacrylamide gel electrophoresis in sodium dodecyl sulfate after reduction and probably have very similar subunit molecular weights. CI globulin apparently consists of two polypeptide chains, each of molecular weight 2.0 x 10(5), held together by disulfide bonds. CI globulin was a substrate for activated fibrin-stabilizing factor (FSF, blood coagulation factor XIII). FSF catalyzed the incorporation of a fluorescent primary amine, N-(5-aminopentyl)-5-dimethylaminonaphthalene-1-sulfonamide, into CI globulin and also catalyzed the cross-linking of CI globulin into multimers, as judged by polyacrylamide gel electrophoresis in sodium dodecyl sulfate after reduction. In the presence of fibrin, cross-linking of CI globulin by FSF occurred without the formation of CI globulin multimers. Instead, polypeptides with apparent molecular weights of 2.6 x 10(5) and 3.0 x 10(5) were seen. The formation of these polypeptides coincided with the loss of the alpha chain of fibrin and CI globulin. The polypeptides were not seen when fibrin alone was cross-linked. The formation of the polypeptides was greater in fine clots than in coarse clots, and greater in clots incubated at 0 degrees than in clots incubated at 37 degrees. In clots made from purified fibrinogen, CI globulin, and FSF, the concentration of CI globulin in the clot liquor was greater if either FSF or calcium ion was omitted and cross-linking did not take place. These observations suggest that CI globulin is enzymically cross-linked to one of the chains of fibrin, most likely the alpha chain, and is thus covalently incorporated into the fibrin clot. CI globulin is very similar to a protein in the plasma membrane of fibroblasts. The cross-linking of CI globulin to itself and to fibrin may typify reactions also involving the fibroblast membrane protein.
冷不溶性球蛋白（CI球蛋白）从人血浆中纯化得到，并根据其沉降系数、电泳迁移率和在正常血浆中的浓度进行鉴定。通过氨基酸分析、从4%琼脂糖上的洗脱位置以及在十二烷基硫酸钠存在下于聚丙烯酰胺凝胶中电泳迁移（无需预先还原），可将CI球蛋白与抗血友病因子（AHF）区分开来。在还原后进行十二烷基硫酸钠聚丙烯酰胺凝胶电泳时，无法区分CI球蛋白和AHF，它们可能具有非常相似的亚基分子量。CI球蛋白显然由两条多肽链组成，每条链的分子量为2.0×10⁵，通过二硫键连接在一起。CI球蛋白是活化纤维蛋白稳定因子（FSF，凝血因子XIII）的底物。FSF催化荧光伯胺N-(5-氨基戊基)-5-二甲基氨基萘-1-磺酰胺掺入CI球蛋白，并催化CI球蛋白交联形成多聚体，这可通过还原后在十二烷基硫酸钠中的聚丙烯酰胺凝胶电泳判断。在有纤维蛋白存在的情况下，FSF使CI球蛋白交联，但未形成CI球蛋白多聚体。相反，出现了表观分子量为2.6×10⁵和3.0×10⁵的多肽。这些多肽的形成与纤维蛋白和CI球蛋白的α链的丢失同时发生。单独交联纤维蛋白时未见到这些多肽。细凝块中多肽的形成比粗凝块中更多，在0℃孵育的凝块中比在37℃孵育的凝块中更多。在由纯化的纤维蛋白原、CI球蛋白和FSF制成的凝块中，如果省略FSF或钙离子且不发生交联，则凝块液中CI球蛋白的浓度更高。这些观察结果表明，CI球蛋白通过酶促作用与纤维蛋白的一条链（很可能是α链）交联，从而共价掺入纤维蛋白凝块中。CI球蛋白与成纤维细胞质膜中的一种蛋白质非常相似。CI球蛋白自身以及与纤维蛋白的交联可能代表了也涉及成纤维细胞膜蛋白的反应。
