Anti-idiotypic antibodies as probes of protein active sites: application to cholera toxin subunit B.
Anti-idiotypic antibodies as probes of protein active sites: application to cholera toxin subunit B.
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抗独特型抗体作为蛋白质活性位点探针：应用于霍乱毒素 B 亚基。
DOI：
10.1073/pnas.84.11.3673
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发表时间：
1987
影响因子：
11.1
通讯作者：
Schoolnik,GK
中科院分区：
文献类型：
--
作者：
Ludwig,DS;Finkelstein,RA;Karu,AE;Dallas,WS;Ashby,ER;Schoolnik,GK
自从Jerne提出免疫调节的“网络”理论以来，抗独特型抗体(anti-IdAB)的性质得到了广泛的研究。针对各种配体的抗体而产生的抗IdAB已被证明与配体的受体结合。因此，抗IdAB的结合部位可能包含有关抗原三维结构的信息。然而，这种“内部图像”的显著特性还没有被用于分子水平的结构研究。在本报告中，针对神经节苷脂GM1(一种结合霍乱毒素的细胞表面糖脂)制备了抗IdAB的单抗，并证明其与霍乱毒素的B亚单位发生交叉反应。推测该抗体识别位于GM1结合区内的氨基酸残基。为了鉴定这些残基，对从产肠毒素的大肠杆菌菌株中纯化的同源毒素和通过重组方法产生的嵌合肽进行了筛选。这些蛋白质N端第4位的氨基酸变异被发现破坏了抗体的结合。由于毒素和嵌合体在结构和功能上都是密切相关的，第4位的残基(霍乱毒素B亚单位中的天冬酰胺)似乎位于抗体的表位中，隐含在GM1结合部位。特别重要的是，这种结构细节不能仅用GM1来推断。配体和反配体反IdAB似乎编码相似的立体化学信息，但使用不同的“化学字母表”，导致不同的结合特异性。
Since Jerne proposed a "network" theory of immune regulation, the properties of anti-idiotypic antibodies (anti-IdAb) have been investigated widely. Anti-IdAb raised against antibodies to a variety of ligands have been shown to bind the ligands' receptors. Thus, the combining site of an anti-IdAb may contain information regarding the three-dimensional structure of an antigen. However, this remarkable property of "internal imagery" has not been exploited for structural investigation at the molecular level. In the present report, a monoclonal "auto"-anti-IdAb was raised against ganglioside GM1 (a cell-surface glycolipid that binds cholera toxin) and was shown to crossreact with the B subunit of cholera toxin. This antibody was presumed to recognize amino acid residues located within the GM1 binding domain. To identify these residues, the antibody was screened against homologous toxins purified from enterotoxigenic strains of Escherichia coli and chimeric peptides produced by recombinant methods. Amino acid variation at position 4 from the N terminus of these proteins was found to disrupt antibody binding. Since the toxins and chimera are all closely related in structure and function, the residue at position 4 (an asparagine in cholera toxin B subunit) appears to be in the epitope of the antibody and, by implication, in the GM1 binding site. Of particular significance, this structural detail could not be deduced with GM1 alone. It would seem that ligand and anti-ligand anti-IdAb encode similar stereochemical information but do so with different "chemical alphabets," giving rise to distinct binding specificities.