Lögdberg L, Björck L
Mol Immunol. 1983 Aug;20(8):885-91. doi: 10.1016/0161-5890(83)90086-x.
The results demonstrate the presence in cod serum of beta 2-microglobulin (beta 2m)-binding molecules. Upon fractionation on Sephadex G-200, the bound beta 2m appears mainly in the void volume, but also as a minor peak with the apparent size of albumin. The complexes show affinity to Con A-Sepharose and Lens culinaris lectin-Sepharose, respectively, indicating that they contain glycoproteins. Because of the high molecular weight of the beta 2m-containing complexes they can be separated from unbound beta 2m by polyethyleneglycol (PEG-6000) precipitation, thus allowing rapid analysis. These beta 2m-binding molecules exhibited size- and charge-homogeneity when separated by gel filtration (Sepharose 4B) and by ion-exchange chromatography (DEAE-cellulose), respectively. The binding is temperature-dependent. At 37 degrees C, maximum binding is reached after about 2 hr. The dissociation is considerably slower, complete dissociation taking about 2 days. According to Scatchard analysis, the association constant is of the order 2 X 10(9)/M. The binding is sensitive to denaturating agents and high salt concentrations. Optimum binding is seen at neutral pH and the beta 2m-binding activity is heat-labile at 50 degrees C. The binding of heterologous beta 2m by cod serum can be used as a cross-reactive assay specific for the detection of beta 2m. Whereas unlabelled human, guinea-pig, and rat beta 2m all give similar inhibition, higher concentrations of rabbit beta 2m are needed for the same degree of inhibition.
结果表明，鳕鱼血清中存在β2-微球蛋白（β2m）结合分子。在Sephadex G - 200上进行分级分离时，结合的β2m主要出现在空体积中，但也有一个较小的峰，其表观大小与白蛋白相当。这些复合物分别对Con A - Sepharose和扁豆凝集素 - Sepharose有亲和力，表明它们含有糖蛋白。由于含β2m复合物的分子量较大，它们可以通过聚乙二醇（PEG - 6000）沉淀与未结合的β2m分离，从而实现快速分析。当通过凝胶过滤（Sepharose 4B）和离子交换色谱（DEAE - 纤维素）分别分离时，这些β2m结合分子表现出大小和电荷均一性。结合作用与温度有关。在37℃时，约2小时后达到最大结合。解离则相当缓慢，完全解离大约需要2天。根据Scatchard分析，缔合常数约为2×10⁹/M。结合作用对变性剂和高盐浓度敏感。在中性pH下观察到最佳结合，并且β2m结合活性在50℃时对热不稳定。鳕鱼血清对异源β2m的结合可作为检测β2m的特异性交叉反应测定法。未标记的人、豚鼠和大鼠β2m都能产生相似的抑制作用，而相同程度的抑制则需要更高浓度的兔β2m。
