High affinity binding of the Entamoeba histolytica lectin to polyvalent n-acetylgalactosaminides

Pablo Adler, Sheila J. Wood, Yuan C. Lee, Reiko T. Lee, William A. Petri, Ronald L. Schnaar

Research output: Contribution to journalArticlepeer-review

Abstract

Entamoeba histolytica trophozoites initiate pathogenic colonization by adherence to host glycoconjugates via an amebic surface lectin which binds to galactose (Gal) and N-acetylgalactosamine (GalNAc) residues. Monovalent and multivalent carbohydrate ligands were screened for inhibition of E. histolytica lectin-mediated human red cell hemagglutination, revealing that: (i) the synthetic multivalent neoglycoprotein GalNAc39BSA (having an average of 39 GalNAc residues linked to bovine serum albumin) was 140,000-fold more potent an inhibitor than monovalent GalNAc and 500,000-fold more potent than monovalent Gal; and (ii) small synthetic multivalent ligands which bind with high affinity to the mammalian hepatic Gal/GalNAc lectin do not bind with high affinity to the E. histolytica lectin. Radioligand binding studies revealed saturable binding of 125I-GalNAc39BSA to E. histolytica membranes (KD = 10 ± 3 nM, Bmax = 0.9 ± 0.08 pmol/mg membrane protein). Maximal binding required the presence of calcium chloride (300 μM) or sodium chloride (50 mM), and had a broad pH maximum (pH 6-9). GalNAc39BSA was 200,000-fold more potent than monovalent GaINAc in blocking radioligand binding. Among synthetic saccharide-derivatized linear polymers, the GalNAcβ and GalNAcα3Galβ derivatives were the most potent, with GalNAcα and GalNAcα3(Fucα2)Galβ derivatives much weaker. The data support a model in which a unique pattern of spaced multiple GalNAc residues are the highest affinity targets for the E. histolytica lectin.

Original languageEnglish (US)
Pages (from-to)5164-5171
Number of pages8
JournalJournal of Biological Chemistry
Volume270
Issue number10
DOIs
StatePublished - Mar 10 1995

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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