文章基本信息

标题：An Active Derivative of Rabbit Antibody Light Chain Composed of the Constant and the Variable Domains Held Together Only by a Native Disulfide Bond
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作者：Knud Poulsen ; Kevin J. Fraser ; Edgar Haber 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1972
卷号：69
期号：9
页码：2495-2499
DOI：10.1073/pnas.69.9.2495
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The immunoglobulin light chain is thought to be organized into two structural domains, the constant and the variable regions, linked by a switch region of lesser tertiary organization. Light chains of homogeneous rabbit antibodies to pneumococcal polysaccharides labeled with 125I were subjected to trypsin digestion at different temperatures. At 43{degrees} molecular size (as determined by gel filtration) remained unchanged until the chain was subjected to full reduction and alkylation, when half molecules were demonstrated. One light chain resisted tryptic digestion at 43{degrees}. At 50{degrees} extensive digestion to small peptides occurred. These experiments confirm the susceptibility of the switch region to enzymatic attack as well as the relative resistance of the constant and variable region domains. They also demonstrate that the third disulfide bridge in rabbit light chain extends between the two structural domains and maintains the integrity of the molecule even when a peptide bond in the switch region is cleaved. When the light chain was subjected to dilute acid hydrolysis [10% acetic acid-pyridine (pH 2.5) in 7 M guanidine-HCl for 24-90 hr] selective cleavage at the switch region was demonstrated in yields up to 90%. The site of cleavage was shown to be the acid labile Asp 109-Pro 110 bond by automated Edman degradation. After cleavage the molecule remained intact until full reduction and alkylation, when half molecules were again demonstrated. A light chain cleaved in this way with its interdomain disulfide bond intact, was able to recombine with a homologous heavy chain and restore antigen binding. This indicates that an intact switch region is not needed for antibody activity. The availability of a functional variable region now allows for planning an examination of the antibody combining site by the technique of peptide synthesis.
关键词：amino-acid sequence ; antibody activity ; limited peptide cleavage ; antibody combining site