Vidal M A, Conde F P
Immunol Commun. 1984;13(5):419-31. doi: 10.3109/08820138409033888.
The protein A-binding site of human IgM was studied by affinity chromatography on SpA-Sepharose using fragments derived from a human monoclonal SpA-reactive IgM, Iz. Neither Fabmu nor (Fc) 5mu fragments were retained on the column but IgM reactivity was unaffected by thermic treatment during proteolysis. Products intermediate between IgM and (Fc) 5mu fragments produced during shorter proteolysis showed a reactivity related to their content in Fabmu regions. On the other hand mild reduction of IgM Iz to monomeric subunits results in a dramatic loss of SpA-affinity. However these subunits, like F(ab') 2mu but unlike Fab'mu fragments, showed a significant interaction with the column. Thus, the principal requirement for SpA reactivity with IgM Iz seems to be related to the presence of Fabmu regions in a polymeric state resembling native IgM.
利用源自人单克隆SpA反应性IgM（Iz）的片段，通过在SpA-琼脂糖凝胶上进行亲和层析，对人IgM的蛋白A结合位点进行了研究。Fabμ片段和（Fc）5μ片段均未保留在柱上，但IgM反应性在蛋白水解过程中不受热处理的影响。在较短蛋白水解过程中产生的介于IgM和（Fc）5μ片段之间的产物，其反应性与其Fabμ区域的含量相关。另一方面，将IgM Iz轻度还原为单体亚基会导致SpA亲和力急剧丧失。然而，这些亚基与F（ab'）2μ一样，但与Fab'μ片段不同，显示出与柱有显著相互作用。因此，SpA与IgM Iz反应的主要要求似乎与处于类似于天然IgM的聚合状态的Fabμ区域的存在有关。
