Studies of the ligand binding to cholera toxin, II. The hydrophilic moiety of sialoglycolipids.

The binding between cholera toxin or its B-protein subunit and various ganglioside-related oligosaccharides was studied by equilibrium displacement dialysis. At low concentrations of ligand, the binding of monosialo-gangliotetraitol exceeded that of the parent ganglioside II3NeuAcGgOse4-Cer, the possible cell surface receptor for the toxin. The terminal galactose residue and an intact carboxyl group of the sialic acid moiety of monosialo-gangliotetraose were found to be necessary for strong binding to the toxin.