Lebreton J P, Rousseaux J, Fontaine M, Ropartz C, Dautrevaux M, Biserte G
Biochim Biophys Acta. 1976 Aug 9;439(2):274-91. doi: 10.1016/0005-2795(76)90063-5.
The inter H-H cysteinyl peptides and the localization of the J-chain were studied in a human F(c)5mu-like fragment. The latter was found to be built up by non-covalent association of molecular forms of 140 000, 95 000 and 70 000 dalton subunits. The trimeric, dimeric and monomeric forms were obtained from gradual reduction by dithiothreitol of the major component of 140 000 daltons, thus confirming the tetrameric nature of this subunit. The latter was found to result from the association of both components of the 70 000 dalton subunit, with the participation of the inter H-H subunit bridge. Structural analysis of the labelled peptides obtained by partial reduction and alkylation showed the presence of the intersubunit disulfide bridge and of the inter heavy-heavy chain bridge of the C-terminal region, and the absence of the heavy-heavy chain bridge of the hinge region. The sequence of these peptides is identical to the sequences of the corresponding peptides of normal mmu-chains. The J-chain, which was covalently linked to this F(c)5mu-like fragment, was found to be predominantly associated within the 95 000 dalton subunit. The results showed that the J-chain was linked in the protein as a "clasp" within a single subunit and not between two subunits.
在人F(c)5μ样片段中研究了H-H间半胱氨酸肽和J链的定位。发现后者由140000、95000和70000道尔顿亚基的分子形式通过非共价结合形成。通过用二硫苏糖醇逐步还原140000道尔顿的主要成分获得三聚体、二聚体和单体形式，从而证实了该亚基的四聚体性质。发现后者是由70000道尔顿亚基的两个成分在H-H间亚基桥的参与下缔合而成。通过部分还原和烷基化获得的标记肽的结构分析表明存在亚基间二硫键和C末端区域的重链间桥，而铰链区的重链间桥不存在。这些肽的序列与正常μm链相应肽的序列相同。发现与该F(c)5μ样片段共价连接的J链主要与95000道尔顿亚基相关联。结果表明，J链在蛋白质中作为“扣环”连接在单个亚基内，而不是在两个亚基之间。
