Binding specificity of a human leucocyte carbohydrate-binding protein.

The binding site specificity of a carbohydrate-binding protein (CBP) synthesized in vitro by normal human peripheral leucocytes was analyzed by affinity chromatography on asialofetuin-Sepharose. Radiolabelled cell extracts were applied to affinity columns. After washing with buffer, the columns were eluted with varying concentrations of different saccharides. The results show that lactose and thiodigalactoside were two of the best inhibitors of CBP binding to asialofetuin. The weakest inhibitors were methyl-beta-D-galactoside and raffinose. Binding of galactose to the CBP was enhanced by the presence of p-NO2-phenyl aglycones. Saccharides unrelated to the D-galactosyl residue failed to inhibit the CBP. Heat-inactivated plasma appeared to have little, if any, binding inhibitors. Binding of CBP to asialofetuin appeared to be inhibited by amine-containing compounds.