Polystyrene‐Adsorbed Gangliosides for Investigation of the Structure of the Tetanus‐Toxin Receptor

Abstract

This paper describes the elaboration, using cholera toxin and GM ganglioside as a model system, of versatile, sensitive methods allowing simple determinations of the specific binding of protein ligands to polystyrene‐adsorbed gangliosides, and, secondly, the application of these methods to the tentative identification of the receptor structure for tetanus toxin. The adsorption characteristics and the ligand‐binding properties of the adsorbed gangliosides were determined, and the specificity and sensitivity of the various ligand‐detection methods (radio‐isotope; enzyme‐linked antibody or water‐vapour condensation) defined. The adsorption did not vary with the type of ganglioside and was found to be linearly proportional to the square root of the incubation concentration and to the log of the incubation time. No difference in adsorption was seen between temperatures of 4 to 37 deg;C. As analyzed with cholera toxin, the polystyrene‐adsorbed ganglioside was structurally specific in binding; i.e. only GM1 was active while after hydrolysis by Vibrio cholerae sialidase also GD1a, GD1b and GT1b, for example, had the same activity as GM1. The affinity of cholera toxin for polystyrene‐adsorbed GM1 was similar to that for viable cells (Ka= 1.2 nM−1). Tetanus toxin was found to bind specifically to gangliosides of the G1b series (GD1b, GT1b and GQ1b) and though with less affinity, also to GT1a, GM1, GD1a and GD3. The binding affinity of tetanus toxin for the G1b gangliosides was less than that of cholera toxin for GM1. The studies showed that tetanus toxin has specific binding affinity for tetraose‐gangliosides with a disialosyl group linked to the inner galactose. It is conceivable that the natural binding structure for the tetanus toxin has the end sequence Galβ1 → 3Ga1NAcβ1 → 4Ga1(2← 8αNeuAc2 ← 3αNeuAc) which occurs in the ganglioside G1b series and possibly also in the oligosaccharide chains of certain cell membrane glycoproteins. Copyright © 1980, Wiley Blackwell. All rights reserved