Binding of mammalian beta sub(2)-microglobulin by glycoproteins in fish serum

The results demonstrate the presence in cod serum of beta sub(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. The binding is temperature-dependent. The dissociation is considerably slower, complete dissociation taking about 2 days. According to Scatchard analysis, the association constant is of the order 2 Chi 10 super(9)/M. The binding is sensitive to denaturing agents and high salt concentrations. Optimum binding is seen at neutral pH and beta 2m-binding activity is heat-labile at 50 degree 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 vie similar inhibition, higher concentrations of rabbit beta 2m are needed for the same degree of inhibition.