Relative affinities of bovine brain 14 kDa galactose lectin binding to individual endogenous gangliosides.

Sugar-specific binding of bovine brain 14 kDa galactose-binding lectin (BBL) to individual endogenous gangliosides (GM1, GM2, GD1a, GD1b and GT1b) was studied using affinity electrophoresis of ganglioside-lectin mixture in polyacrylamide gel at pH 8.3. Unbound (free) lectin moved ahead while ganglioside-lectin complex moved very little. Sugar-specificity of binding was confirmed by reversal of the interaction by (i) presence of lactose along with the lectin and (ii) pretreatment of gangliosides with another galactose-binding lectin, Ricinus communis agglutinin. Stoichiometry of ganglioside-BBL interaction revealed that GT1b had the highest affinity for the lectin followed by GD1b and GM2, while GM1 and GD1a had the least affinity. Results indicated that a terminal sialic acid moiety covering a galactose moiety may at times enhance BBL recognition of the latter and that changes in ganglioside pattern is a possible modulator of lectin function in vivo.