Carbohydrate specificity of the receptor sites of mistletoe toxic lectin-I

The carbohydrate specificity of mistletoe toxic lectin-I (ML-I) was studied by haemagglutination-inhibition assay. The results indicated that ML-I has a broad range of affinity for Gal, α, β linked sequences. The galabiose (C, Galα1→4Gal) sequence, a receptor of the uropathogenic E. coli ligand, was one of the best disaccharide inhibitors tested. The lectin also exhibits affinity for Lac(Galβ1→4Glc), T(Galβ1→3GalNAc), I/II(Galβ1→3/4GlcNAc) and B(Galα1→3Gal) sequences. Galα1→4Gal and Galβ1→4Glc are frequently occurring sequences of many glycosphingolipids located at the mammalian cell membranes, such as intestinal and red blood cell membranes, for ligand binding and toxin attachment. This finding provides important information concerning the possible mechanism of intoxication of cells by the mistletoe preparation.