Plow E F, Edgington T S
J Biol Chem. 1975 May 10;250(9):3386-92.
The E fragment, derived from the NH2-terminal aspect of fibrinogen by plasmin cleavage (fg-E), possesses two generically distinct sets of antigenic expressions. The major set of antigens is expressed by the parent molecule as indicated by the capacity of a major subpopulation of antibodies present in antiserum to fg-E and reactive with fg-E to: (a) react with fibrinogen, and (b) be specifically absorbed by fibrinogen but appears following proteolysis with plasmin. These cleavage associated neoantigens (fg-E-neo) specifically react with a minor subpopulation of antibodies present in antiserum to fg-E.E fragments isolated after varying exposures to plasmin all expressed fg-E-neo, but early E fragments exhibited quantitatively less neoantigenic expression than more extensively degraded E fragments. The entire fg-E-neo expression is recovered on a single isolated constituent chain of the E fragment, and immunochemical analysis with antiserum to the isolated constituent chain-bearing fg-E-neo identifies it as a derivative of the gamma chain constituent, exhibits marked stability to physicochemical denaturation and enzymatic degradation. These properties suggest that the neoantigen may be associated with a specific amino acid sequence which is exposed by the cleavage process. The identification and localization of fg-E-neo provides a specific molecular marker site for the characterization of structural and conformational changes associated with catabolism and function of fibrinogen.
E片段由纤溶酶裂解纤维蛋白原的NH2末端产生（fg-E），具有两组一般不同的抗原表达。主要的抗原组由亲本分子表达，这由抗fg-E血清中存在的主要抗体亚群与fg-E反应的能力表明：（a）与纤维蛋白原反应，（b）被纤维蛋白原特异性吸收，但在纤溶酶蛋白水解后出现。这些裂解相关的新抗原（fg-E-neo）与抗fg-E血清中存在的次要抗体亚群特异性反应。在不同暴露于纤溶酶后分离的E片段均表达fg-E-neo，但早期E片段的新抗原表达量比降解更广泛的E片段少。整个fg-E-neo表达在E片段的单个分离组成链上恢复，用抗带有fg-E-neo的分离组成链的血清进行免疫化学分析，将其鉴定为γ链组成部分的衍生物，对物理化学变性和酶促降解表现出显著稳定性。这些特性表明新抗原可能与裂解过程中暴露的特定氨基酸序列相关。fg-E-neo的鉴定和定位为表征与纤维蛋白原分解代谢和功能相关的结构和构象变化提供了一个特定的分子标记位点。
