The binding properties of human Tamm-Horsfall Sd(a+) urinary glycoprotein (THGP) and asialo-THGP with Triticum vulgaris agglutinin(WGA) and three toxic lectins (abrin-a, ricin, and Mistletoe toxic lectin-I) were investigated by quantitative precipitin and precipitin inhibition assays. Both glycoproteins reacted strongly with abrin-a, precipitating over 80% of the lectin nitrogen tested. THGP also bound well to mistletoe toxic lectin-I and precipitated 86% of this lectin added, while the precipitability of its asialo product decreased by 28%. The native glycoprotein completely precipitated the WGA added, but its reactivity was reduced dramatically after desialylation. On the contrary, the poor reactivity of THGP with ricin increased substantially after removal of sialic acid and completely precipitated the lectin added. The glycoprotein-lectin interactions were inhibited by one or several of the following haptens, p-NO2-phenylaGaiNAc, p-NO2-phenyl~GalNAc, Gal~l--~4GlcNAc, Gallgl-->4GIc, GlcNAc/]l--~4GIcNAc and/or GIcNAc. From the above results, it is concluded that native and/or asialo Tamm-Horsfall glycoproteins serve as important receptors for these three toxic lectins and for WGA.Key words: Lectin reactivity of abrin-a, ricin, ML-I and wheat germ; Native and asialo-Tamm-Horsfall glycoproteins charides ranging from nonfucosylated, monosialylated diantennary chains to fucosylated, tetrasialylated, tetraantennary chains [4]. Most Tamm-Horsfall glycoproteins carry the Sd(a+) blood group active determinant, GalNAcfll 4(NeuAcc~2 --. 3)Galfll ~ 4GlcNAcfll --* 3Gal, indicating the presence of a repeating N-acetyllactosamine unit [5,6], but the rare phenotype Sd(a-) lacks the terminal GalNAc residue [6,7].THGP inhibits the mannose-dependent adhesion of Escherichia coli [1,2,8,9] and is a member of a structural glycoprotein family known to modulate cell adhesion [1]. However, little is known about the binding properties of THGP with toxic biomolecules, and/or the roles of sialic acid, N-acetyllactosamine, and chitin disaccharide (GlcNAcfll --*4GIcNAc, at the ends of the N-linked chains in the linkage region to the peptide) in the interaction of THGP with lectins. In this report, we characterized the binding properties of THGP, before and after mild acid hydrolysis, with three toxic lectins and Triticum vulgaris (WGA) agglutinin by both quantitative precipitin and precipitin inhibition assays.The results suggest that the Sd(a +) THGP and/or its desialylated product contain important receptors for WGA and for three toxic lectins (abrin-a, ricin, and ML-I).
Studies on the structures and binding properties of the glycoproteins, purified from human ovarian cyst fluids, will aid the understanding of the carbohydrate alterations occurring during the biosynthesis of blood group antigens and neoplasm formation. These glycoproteins can also serve as important biological materials to study blood group A, B, H, Le(a), Le(b), Le(x), Le(y), T and Tn determinants, precursor type I and II sequences and cold agglutinin I and i epitopes. In this study, the binding property of a cyst glycoprotein from a human blood group Le(a+) nonsecretor individual, that contains an unusually high amount (18%) of sialic acid (HOC 350) was characterized by quantitative precipitin assay with a panel of lectins exhibiting a broad range of carbohydrate-binding specificities. Native HOC 350 reacted well only with three out of nineteen lectins tested. It precipitated about 80% of Ricinus communis (RCA1), 50% of Triticum vulgaris (WGA) and 37% of Bauhinia purpurea aba (BPA) agglutinins, respectively. However, its asialo product had dramatically enhanced reactivity and reacted well with many I/II (Gal beta1 --> 3/4GcNAc), T(Gal beta1 --> 3GalNAc) and Tn(GaNIAc alphaI --> Ser/Thr) active lectins. It bound best to Jacalin, BPA, and abrin-a and completely precipitated all the lectins added. Asialo-HOC 350 also reacted strongly with Wistaria floribunda, Abrus precatorius agglutinin, ricin and RCA1 and precipitated over 75% of the lectin nitrogen added, and moderately with Arachis hypogaea, Maclura pomifera, WGA, Vicia viosa-B4, Codium fragile tomentosoides and Ulex europaeus-II. But native HOC 350 and its asialo product reacted not at all or poorly with Dolichos biflorus, Helix pomatia, Lotus tetra-gonolobus, Ulex europaeus-I, Lens culinaris lectins and Con A. The lectin-glycoform interactions through bioactive sugars were confirmed by precipitin inhibition assay. Mapping the precipitation profiles of the interactions have led to the conclusion that HOC 350 contains a large number of receptors for I/II, T, and Tn active lectins. But in the untreated (or native) substance, most of these determinants are masked by sialic acids.
The binding patterns of human blood group Sd(a+) and Sd(a3) Tamm-Horsfall glycoproteins (THGPs) with respect to four GalNAc specific agglutinins were studied by quantitative precipitin assay (QPA) and enzyme linked lectinosorbent assay (ELLSA). Of the native and asialo Sd(a+) and Sd(a3) THGP tested by QPA and ELLSA, only native and asialo Sd(a+) bound well with Dolichos biflorus (DBA) and Vicia villosa-B R (VVA-B R ), while Sd(a3) THGP reacted poorly with these two lectins. Neither Sd(a+) nor Sd(a3) THGPs reacted with two other GalNAc K K-anomer specific lectins: Codium fragile subspecies tomentosoides and Artocarpus integrifolia. Furthermore, the binding of asialo Sd(a+)THGP-VVA-B R and native Sd(a+)THGP-DBA through GalNAcL LC was confirmed by inhibition assay. These results demonstrate that DBA and VVA-B R are useful reagents to differentiate between Sd(a+) and Sd(a3) THGP.z 1998 Federation of European Biochemical Societies.
Unlike the human blood group Sd(a+) Tamm-Horsfall glycoprotein (THGP), the Sd(a-) one lacks terminal GalNAc[~I--, residues at the nonreducing ends. The binding properties of this glycoprotein and its asialo product with lectins were characterized by quantitative precipitin (QPA) and precipitin inhibition assays. Among 20 lectins tested by QPA, both native and asialo Sd(a-) THGP reacted best with Abrus precatorius and Ricinus communis and completely precipitated the lectin added. They also precipitated well Wistariafloribunda (WFA), Glycine max (SBA), Bauhinia purpurea alba, abrin-a and ricin, all of which recognize the Gall31--, 4GIcNAc[~I--, sequence, although at different strength. The lectin-glyean interactions were inhibited by GaI[~I~4GIcNAc and Gal[~l --* 4Glc. When the precipitability of Sd(a-) THGP was compared with that of the Sd(a+) phenotype, the native Sd(a-) THGP exhibited a 40% lesser affinity for WFA, SBA, WGA and mistletoe lectin-I (ML-I). Mapping the precipitation and inhibition profiles of the present study and the results of THGP Sd(a+), it is concluded that Sd(a-) THGP showed a strongly diminished affinity for GalNAcl31-~ active lectins (SBA and WFA) than the Sd(a+) phenotype.
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