Human C4-binding protein. II. Role in proteolysis of C4b by C3b-inactivator.
Human C4-binding protein. II. Role in proteolysis of C4b by C3b-inactivator.
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人C4结合蛋白。 ii。 C3B灭活剂在C4B蛋白水解中的作用。
DOI：
10.1084/jem.148.4.1044
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发表时间：
1978-10-01
期刊：
影响因子：
--
通讯作者：
Nussenzweig V
中科院分区：
文献类型：
--
作者：
Fujita T;Gigli I;Nussenzweig V
我们最近描述了从人血清中分离的高分子量蛋白质与液相活化C4的特异性结合亲和力。我们在这里表明，C4结合蛋白（C4-Bp）的功能作为一个重要的辅助因子在C4 b的蛋白水解的C3 b灭活剂（C3 bINA）的存在下。C4-bp与C3 bINA一起将C4 b的α '链切割成三个片段，称为α 2、α 3和α 4，分子量分别为47，000、25，000和17，000道尔顿。α 2片段与C4 b解离而不还原，而α 3和α 4片段与C4 b的其他链二硫键结合。当省略C4-bp或C3 bINA时，或者在任一蛋白质与beta1 H组合存在的情况下，该反应都不会发生。天然C4不受C3 bINA a和C4- bp的影响。当在C3 bINA遗传缺陷患者的血清中孵育时，C4 b没有被切割。然而，当加入纯化的C3 bINA时，C4 b的α ′-链被切割，并产生与α 2、α 3和α 4具有相同分子量的片段。
We recently described the isolation from human serum of a high molecular weight protein with specific binding affinity for fluid-phase activated C4. We show here that the C4-binding protein (C4-Bp) functions as an essential cofactor in the proteolysis of C4b in the presence of C3b-inactivator (C3bINA). C4-bp, together with C3bINA, cleave the alpha'-chain of C4b into three fragments called alpha2, alpha3, and alpha4, with mol wt of 47,000, 25,000, and 17,000 daltons, respectively. The alpha2 fragment was dissociated from C4b without reduction, whereas the alpha3 and alpha4 fragments were disulfide bonded the other chains of C4b. The reaction did not occur when either C4-bp or C3bINA were omitted, nor in the presence of either protein in combination with beta1H. Native C4 was not affected by C3bINA aand C4- bp. C4b was not cleaved when incubated in serum of a patient with genetic deficiency of C3bINA. However, when purified C3bINA was added, the alpha'-chain of C4b was cleaved and fragments with the same molecular weight as alpha2, alpha3, and alpha4 were generated.