Studies on the binding substances on human erythrocytes for the heat-labile enterotoxin isolated from porcine enterotoxigenic Escherichia coli.
The binding substance for the heat-labile enterotoxin (LTp) isolated from porcine enterotoxigenic Escherichia coli was studied by competitive binding assays. The binding of 125I-labeled LTp to neuraminidase-treated human type A erythrocytes was most effectively inhibited by ganglioside GM1 among inhibitors used. Mono-, di- and polysaccharides, glycoproteins and lectins were over 10(4)-times less potent inhibitors. Similar results were also obtained in competitive binding assays with 3H-labeled ganglioside GM1 and LTp-coupled Sepharose 4B. On the other hand, hemagglutination of neuraminidase-treated human type A erythrocytes by LTp was inhibited by methyl alpha-D-galactopyranoside, galactose, melibiose and some glycoproteins, but not effectively inhibited by ganglioside GM1 at the highest concentration used. Preincubation of LTp with an appropriate amount of ganglioside GM1 resulted in much higher hemagglutination than LTp alone. Although these findings show that there may be fundamental differences between interactions with ganglioside GM1 in hemagglutination compared to interactions with ganglioside GM1 in binding, the predominant binding substance for LTp on neuraminidase-treated human type A erythrocytes is suggested to be ganglioside GM1.
Sugii
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Department of Serology and Immunology, School of Medical Technology, Kitasato University, Kanagawa, Japan.
Tsuji
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T
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000032:analysis*; D004768:Enterotoxins / Q000494:pharmacology*; D004912:Erythrocytes / Q000201:enzymology*; D004926:Escherichia coli / Q000378:metabolism*; D005732:Gangliosides / Q000032:analysis*; D006023:Glycoproteins / Q000032:analysis; D006386:Hemagglutination Tests; D006801:Humans; D009439:Neuraminidase / Q000037:antagonists & inhibitors*; D013552:Swine
D002352:Carrier Proteins; D004768:Enterotoxins; D005732:Gangliosides; D006023:Glycoproteins; D009439:Neuraminidase