Milstein C P, Richardson N E, Dieverson E V, Feinstein A
Biochem J. 1975 Dec;151(3):615-24. doi: 10.1042/bj1510615.
Mouse IgM (immunoglobulin M) was selectively and partially reduced and treated with iodo[2-14C]acetate to label the interchain disulphide bridges. The carboxymethylation was studied in some detail. The labelled peptides were purified, sequenced and positioned by homology with human IgM. Only peptides originating from three interchain disulphide bridges were labelled, in contrast with the four labelled bridges obtained in human IgM under the same conditions. These peptides are homologous to human bridge peptides forming the heavy-light bridge and two inter-heavy bridges, one present in the CMU2 region and the other in the C-terminal region. The inter-heavy bridge in the Cmu2 region was alone cleaved and radioactively labelled in selectively reduced IgM held together as a pentamer by non-covalen interactions. The same bridge was the only one to be totally cleaved in subunits released after more extensive, though still selective, reduction. In the light of these results a possible arrangement of the disulphide bridges of the mouse IgM.
小鼠免疫球蛋白M（IgM）被选择性地部分还原，并用碘[2-¹⁴C]乙酸盐处理以标记链间二硫键。对羧甲基化进行了较为详细的研究。纯化、测序标记的肽段，并通过与人类IgM的同源性进行定位。与在相同条件下人类IgM中获得的四个标记桥不同，仅来自三个链间二硫键的肽段被标记。这些肽段与形成重链-轻链桥和两个重链间桥的人类桥肽同源，一个存在于CMU2区域，另一个在C末端区域。在通过非共价相互作用保持为五聚体的选择性还原的IgM中，Cmu2区域的重链间桥单独被切割并放射性标记。在更广泛（尽管仍然是选择性）还原后释放的亚基中，同一桥是唯一完全被切割的桥。根据这些结果，推测了小鼠IgM二硫键的可能排列方式。
