Sugii S, Tsuji T
Department of Serology and Immunology, School of Medical Technology, Kitasato University, Kanagawa, Japan.
Can J Microbiol. 1989 Jun;35(6):670-3. doi: 10.1139/m89-109.
The binding specificities of heat-labile enterotoxins (LTp and LTh) isolated from porcine and human enterotoxigenic Escherichia coli on human erythrocytes were studied by competitive binding assays using different gangliosides as inhibitors. The binding of 125I-labeled LTp to neuraminidase-treated human type A erythrocytes was most effectively inhibited by ganglioside GM1. Ganglioside GM1 was 11 and 105 times more potent than gangliosides GD1b and GM2, respectively. Gangliosides GD1a, GT1b, and GM3 were much less potent. Similar results were also obtained in competitive binding assays with the 125I-labeled B subunit of LTh and neuraminidase-treated human type B erythrocytes, and in those with 3H-labeled ganglioside GM1 and LTp-coupled Sepharose 4B. The binding of 3H-labeled ganglioside GM1 to LTp was not effectively inhibited by galactose-beta(1----3)N-acetyl-D-galactosamine at the highest concentration used. These findings suggest that the combining sites of LTp and LTh may be specific for at least the galactose-N-acetyl-D-galactosamine-galactose (N-acetyl-neuraminic acid) portion of ganglioside GM1.
采用不同神经节苷脂作为抑制剂，通过竞争性结合试验，研究了从猪和人产肠毒素大肠杆菌中分离出的不耐热肠毒素（LTp和LTh）对人红细胞的结合特异性。用神经氨酸酶处理过的人A型红细胞与125I标记的LTp的结合，最有效地被神经节苷脂GM1抑制。神经节苷脂GM1分别比神经节苷脂GD1b和GM2的效力强11倍和105倍。神经节苷脂GD1a、GT1b和GM3的效力则低得多。在用125I标记的LTh的B亚基与经神经氨酸酶处理的人B型红细胞进行的竞争性结合试验中，以及在用3H标记的神经节苷脂GM1与LTp偶联的琼脂糖4B进行的试验中，也得到了类似结果。在所用的最高浓度下，半乳糖-β(1→3)N-乙酰-D-半乳糖胺不能有效抑制3H标记的神经节苷脂GM1与LTp的结合。这些发现表明，LTp和LTh的结合位点可能至少对神经节苷脂GM1的半乳糖-N-乙酰-D-半乳糖胺-半乳糖（N-乙酰神经氨酸）部分具有特异性。
