Binding specificity of the combining site of cholera toxin for human erythrocytes.
The reactivity of cholera toxin (CT) with blood-group determinant(s) on human erythrocytes was studied by competitive binding assays. 125I-labeled CT was found to bind more efficiently to pronase- and neuraminidase-treated human type A, B, and O erythrocytes than their untreated ones. The binding of 125I-labeled CT to neuraminidase-treated human type B erythrocytes was effectively inhibited by ganglioside GM1, but not by porcine gastric mucin with both A and H determinants (hog A + H), blood group specific lectins, and other substances at the highest concentrations used. Ganglioside GM1 was at least 10(5) times more potent than other inhibitors. These findings strongly suggest that the predominant binding substance for CT on human erythrocytes is not the blood-group determinant(s) but ganglioside GM1.
Sugii
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Department of Serology and Immunology, School of Medical Technology, Kitasato University, Kanagawa, Japan.
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001789:Blood Group Antigens; D002772:Cholera Toxin / Q000378:metabolism*; D000939:Epitopes / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005677:G(M1) Ganglioside / Q000378:metabolism*; D005752:Gastric Mucins / Q000378:metabolism; D006801:Humans; D013552:Swine
D001789:Blood Group Antigens; D000939:Epitopes; D005752:Gastric Mucins; D005677:G(M1) Ganglioside; D002772:Cholera Toxin