Abstract
The binding properties of a glycoprotein with blood group Pt specificity isolated from sheep hydatid cyst fluid with Gal and Ga1NAc specific lectins was investigated by quantitative precipitin and precipitin inhibition assays. The glycoprotein completely precipitated Ricinus communis agglutinin (RCA 1). Abrus precatorius agglutinin (APA[ and Mistletoe toxic lectin-I (ML-I). Only 1.0 μg of P 1 glycoprotein was required to precipitate 50% of 5.1 μg ML-I nitrogen. It also reacted well with abrin-a and ricin, precipitating over 73% of the lectin nitrogen added, but poorly or weakly with Dolichos biflorus (DBL), Vicia villosa (VVL, a mixture of A 4, A 2B 2 and B 4), VVL-B 4, Arachis hypogaea (PNA), Maclura pomifera (MPL), Bauhinia purpurea alba (BPL) and Wistaria floribunda (WFL) lectins. When an inhibition assay in the range of 5.1 μgN to 5.9 μgN of lectins (ML-I, abrin-a; ricin, RCA 1 and APA, and 10 μg P 1 active glycoprotein interaction was performed; from 76 to 100% of the precipitations were inhibited by 0.44 and 0.52 μmol of Galα 1 → 4Gal and Galβ1 → 4GlcNAc, respectively, but not or insignificantly with 1.72 μmol of GlcNAc. The Gala 1 → 4Gal disaccharide found in this P 1 active glycoprotein is a frequently occurring sequence of many glycosphingolipids located at the surface of mammalian cell membranes, especially human erythrocytes and intestinal cells for ligand binding and microbial toxin attachment. The present finding suggests that the Galα 1 → 4Galβ1 → 4GlcNAc sequence in this P 1 active glycoprotein is one of the best glycoprotein receptors for three toxic lectins (ricin, abrin-a, and ML-I) as well as for APA, and RCA 1, and the result of inhibition assay implies that these lectins are recognizing part or all of the Galα1 → 4Galβ1 → 4GlcNAc sequence in the P 1 active glycoprotein.
Published Version
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