免疫球蛋白轻链
单体
分泌物
突变体
化学
J链
侧链
差速离心
生物化学
立体化学
生物物理学
生物
抗体
基因
聚合物
有机化学
免疫学
作者
Jeanne L. Dul,S Aviel,J Melnick,Yair Argon
出处
期刊:Journal of Immunology
[The American Association of Immunologists]
日期:1996-10-01
卷期号:157 (7): 2969-2975
被引量:47
标识
DOI:10.4049/jimmunol.157.7.2969
摘要
Ig light (L) chains are secreted not only as part of assembled Ab molecules, but also as free L chains, the latter process being involved in the pathology of several diseases. The secretion competence of free L chains distinguishes them from free subunits of other oligomeric proteins, which are usually retained intracellularly. We used several techniques to test the idea that secretion of free L chains is dependent on dimerization. Coexpression of pairs of L chains, differing in only one amino acid, which alters the secretory phenotype, shows that these L chains behave independently: the wild-type chains are secreted, whereas the mutants are retained intracellularly. A survey of kappa- or lambda-producing cell lines by nonreducing gel electrophoresis shows that a negligible fraction of these L chains exists as disulfide-bonded dimers. Moreover, chemical cross-linking and density gradient centrifugation demonstrate that there is no significant pool of noncovalent L chain dimers. Noncovalent heterodimers can be detected readily between a kappa-chain and a chimera consisting of a heavy chain variable domain linked to the kappa-chain constant domain. This confirms that noncovalent L chain homodimers would have been detected if they were present. These findings about the association state of free L chains are independent of the host cell, as they are observed in both myeloma cells and COS fibroblasts. We conclude that L chain dimerization is a rare event that neither facilitates secretion nor is required for it.
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