The first component of human complement-猫眼课题宝

人体补体的第一个组成部分

DOI：

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发表时间：

1976

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通讯作者：

中科院分区：

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文献类型：

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作者：

Robert B Sim

1.介绍了部分纯化C_1和C_ī的方法，并建立了从C_1和C_ī制剂中分离亚组分C_1r和C_1s的方法。2.1.从C1和Cī衍生的C1R的结构研究表明，C1R和C1s一样，以酶原的形式存在于血清中，通过有限的蛋白水解酶被激活。2.2.C1R和C1S都是分子量为83,000的单一多肽链酶原，氨基酸组成相似。它们在碳水化合物组成和抗原性方面是不同的。C1r和C1s的激活不会丢失糖肽，但可能会丢失小肽。2.3.C1R和C1S每摩尔蛋白质结合一摩尔DFP。C1R和C1S的26,000个二异丙基磷酸结合多肽链的前20个残基的氨基酸序列与丝氨酸蛋白酶的相应区域如胰蛋白酶和纤溶酶具有高度的序列同源性。因此，C1R和C1S被鉴定为丝氨酸蛋白酶，其大小和结构与纤溶酶相似。比较了C1r和C1s与其他丝氨酸蛋白酶酶原的结构和激活方式。3.1.对C1r和C1s的酶活性进行了研究。C1R能裂解C1S，但不能降解任何合成底物。C1S能裂解C2和C4，并能分解几种氨基酸酯。讨论了C1r和C1s的蛋白水解性。3.2.建立了适合于酶原活化动力学研究的C1r和C1s的快速、简便的分析方法。4.1.研究了C1q与C1r和C1s在溶液中或与抗体-抗原复合物结合时的相互作用。4.2.在溶液中，C1r和C1s形成含有2C1r+2C1s分子或4C1r+4C1s分子的强钙依赖性络合物。C1r、C1s和C1r-C1s络合物与C1q相互作用较弱。4.3.当C1q与免疫复合物结合时，C1r和C1r-C1s复合体与C1q强烈结合。在没有C1r 4.4的情况下，C1s不与C1q结合。C1r和C1s的激活似乎不会改变它们与其他亚组分的结合亲和力，无论是在溶液中还是在与抗体-抗原结合时。5.1.研究了C1r和C1s在溶液中的自发活化。C1S不会自动催化激活。没有观察到C1r制剂的绝对稳定性，但结论是C1r的自动激活对C1r的不稳定性没有显著影响。5.2.当固定在抗体-抗原-C1q复合体上时，除非C1s也存在，否则C1r不会被激活。C1S对C1R激活的影响不需要C1S的酶活性，很明显，C1S满足结合要求。5.3.讨论了C_1与免疫复合物相互作用的活化机制。

1. Procedures for partial purification of C1 and Cī are described and methods for the isolation of subcomponents C1r and C1s from C1 and Cī preparations have been developed. 2.1. Structural studies of C1r derived from C1 and Cī have shown that C1r, like C1s, exists in serum as a proenzyme, which is activated by limited proteolysis. 2.2. C1r and C1s are both single polypeptide-chain zymogens of 83,000 molecular weight with similar amino acid compositions. They are distinct in carbohydrate composition and antigenic properties. Activation of C1r and C1s occurs without loss of glycopeptides but loss of small peptides may occur. 2.3. C1r and C1s bind one mole of DFP per mole of protein. The amino acid sequences of the first 20 residues of the 26,000 molecular weight diisopropylphosphate-binding polypeptide chains of C1r and C1s show a high degree of sequence identity with corresponding regions of serine proteases such as trypsin and plasmin. C1r and C1s are therefore identified as serine proteaces of similar size and structure to plasmin. The structure and mode of activation of C1r and C1s and other serine protease zymogens are compared. 3.1. The enzymic activities of C1r and C1s have been investigated. C1r cleaves C1s but did not hydrolyse any synthetic substrate tested. C1s cleaves C2 and C4 and hydrolyses several amino acid esters. The proteolytic specificities of C1r and C1s are discussed. 3.2. Rapid and convenient assays for C1r and C1s, suitable for kinetic studies of zymogen activation, have been developed. 4.1. The interactions of C1q, in solution or bound to antibody-antigen complexes, with C1r and C1s have been examined. 4.2. In solution, C1r and C1s form strong Ca 2+ -dependent complexes containing 2C1r + 2C1s molecules, or 4C1r + 4C1s molecules. C1r, C1s and the C1r-C1s complexes interact weakly with C1q. 4.3. When C1q is bound to immune complexes, C1r and C1r-C1s complexes bind strongly to C1q. C1s does not bind to C1q in the absence of C1r 4.4. Activation of C1r and C1s does not appear to alter their binding affinity for other subcomponents either in solution or when bound to antibody-antigen. 5.1. Spontaneous activation of C1r and C1s in solution has been studied. C1s does not activate autocatalytically. Absolute stability of C1r preparations was not observed, but it is concluded that auto-activation of C1r does not contribute significantly to the instability of C1r. 5.2. When fixed to antibody-antigen-C1q complexes, C1r does not activate unless C1s is also present. The effect of C1s on C1r activation does not require C1s enzymic activity and it is apparent that C1s fulfills a binding requirement. 5.3. The mechanism of activation of C1 on interaction with immune complexes is discussed.