Carboxyl-terminal portions of the alpha chains of fibrinogen and fibrin. Localization by electron microscopy and the effects of isolated alpha C fragments on polymerization.
Carboxyl-terminal portions of the alpha chains of fibrinogen and fibrin. Localization by electron microscopy and the effects of isolated alpha C fragments on polymerization.
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DOI：
10.1016/s0021-9258(19)38688-0
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发表时间：
1993-06
期刊：
影响因子：
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通讯作者：
Y. Veklich;O. Gorkun;L. Medved;W. Nieuwenhuizen;J. Weisel
中科院分区：
文献类型：
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作者：
Y. Veklich;O. Gorkun;L. Medved;W. Nieuwenhuizen;J. Weisel
通过旋转阴影制剂的电子显微镜测定纤维蛋白原及其一些衍生物的 A α 链的羧基末端三分之二或 α C 结构域的位置。针对 A α 链羧基端 150 个氨基酸的单克隆抗体 G8 结合在纤维蛋白原的中心区域附近，表明大多数分子的 α C 结构域通常不可见，因为它们位于氨基端二硫键上或附近。在 pH 3.5 时，纤维蛋白原和纤维蛋白单体似乎相似，大多数分子两端都有一个小球状结构域。相比之下，通过用纤溶酶从纤维蛋白原裂解αC结构域产生的片段X单体则没有显示出这样的投射。当纤维蛋白单体在聚合延迟的条件下达到中性 pH 值时，单个分子仍然可见，将 α C 结构域显示为中心区域附近的单个附加结节。此外，对分子簇的分析揭示了通过 α C 结构域的一些分子间关联。包含 α C 结构域的 40-kDa 片段已从纤维蛋白原的纤溶酶消化物中分离出来，并通过 SDS 聚丙烯酰胺凝胶电泳和氨基末端氨基酸序列的测定进行表征。 α C 片段的电子显微镜揭示了单个球状结构以及寡聚体聚集体。将 α C 片段添加到纤维蛋白单体中，然后稀释至中性 pH 值以引发聚合，会导致较低的浊度、较长的滞后期和较慢的浊度增加最大速率。此外，电子显微镜揭示了 α C 片段与纤维蛋白单体在中性 pH 下的复合物。看来游离的 α C 片段可以与纤维蛋白的 α C 结构域结合，与参与聚合的正常 α C 结构域相互作用竞争。
The locations of the carboxyl-terminal two thirds of the A alpha chains, or the alpha C domains, were determined for fibrinogen and some of its derivatives by electron microscopy of rotary-shadowed preparations. A monoclonal antibody, G8, to the carboxyl-terminal 150 amino acids of the A alpha chain, binds near the central region of fibrinogen, indicating that the alpha C domains of most molecules are not normally visible because they are on or near the amino-terminal disulfide knot. At pH 3.5, fibrinogen and fibrin monomers appear to be similar, with a projection terminating in a small globular domain from each end of most molecules. In contrast, fragment X monomers, produced by cleavage of the alpha C domains from fibrinogen with plasmin, show no such projections. When fibrin monomer is brought to neutral pH under conditions where polymerization is delayed, individual molecules are still visible showing the alpha C domains as a single additional nodule near the central region. Moreover, analysis of clusters of molecules reveals some intermolecular associations via the alpha C domains. A 40-kDa fragment comprising the alpha C domain has been isolated from a plasmin digest of fibrinogen and characterized by SDS-polyacrylamide gel electrophoresis and determination of amino-terminal amino acid sequences. Electron microscopy of alpha C fragments reveals individual globular structures, as well as oligomeric aggregates. The addition of alpha C fragments to fibrin monomer followed by dilution to neutral pH to initiate polymerization results in lower turbidity, longer lag period, and slower maximum rate of turbidity increase. Also, electron microscopy reveals complexes of alpha C fragments with fibrin monomer at neutral pH. It appears that the free alpha C fragments can bind to the alpha C domains of fibrin, competing with the normal alpha C domain interactions involved in polymerization.