title: Binding of polysaccharides to human galectin-3 at a noncanonical site in its carbohydrate recognition domain.
abstract: Galectin-3 (Gal-3) is a multifunctional lectin, unique to galectins by the presence of a long N-terminal tail (NT) off of its carbohydrate recognition domain (CRD). Many previous studies have investigated binding of small carbohydrates to its CRD. Here, we used nuclear magnetic resonance spectroscopy ((15)N-(1)H heteronuclear single quantum coherence data) to assess binding of (15)N-Gal-3 (and truncated (15)N-Gal-3 CRD) to several, relatively large polysaccharides, including eight varieties of galactomannans (GMs), as well as a β(1 → 4)-polymannan and an α-branched mannan. Overall, we found that these polysaccharides with a larger carbohydrate footprint interact primarily with a noncanonical carbohydrate-binding site on the F-face of the Gal-3 CRD β-sandwich, and to a less extent, if at all, with the canonical carbohydrate-binding site on the S-face. While there is no evidence for interaction with the NT itself, it does appear that the NT somehow mediates stronger interactions between the Gal-3 CRD and the GMs. Significant Gal-3 resonance broadening observed during polysaccharide titrations indicates that interactions occur in the intermediate exchange regime, and analysis of these data allows estimation of affinities and stoichiometries that range from 4 × 10(4) to 12 × 10(4) M(-1) per site and multiple sites per polysaccharide, respectively. We also found that lactose can still bind to the CRD S-face of GM-bound Gal-3, with the binding of one ligand attenuating affinity of the other. These data are compared with previous results on Gal-1, revealing differences and similarities. They also provide research direction to the development of these polysaccharides as galectin-targeting therapeutics in the clinic.
authors.affiliation: Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Health Sciences Center, 6-155 Jackson Hall, 321 Church Street, Minneapolis, MN 55455, USA.
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Miller
authors.affiliation: Department of Biochemistry and CARIM, University of Maastricht, 6229 ER Maastricht, The Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Ippel
authors.affiliation: Department of Biochemistry and CARIM, University of Maastricht, 6229 ER Maastricht, The Netherlands.
authors.forename: Dennis
authors.initials: D
authors.lastname: Suylen
authors.affiliation: Galectin Therapeutics, 4960 Peachtree Industrial Blvd., Suite 240, Norcross, GA 30071, USA.
authors.forename: Anatole A
authors.initials: AA
authors.lastname: Klyosov
authors.affiliation: Galectin Therapeutics, 4960 Peachtree Industrial Blvd., Suite 240, Norcross, GA 30071, USA.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Traber
authors.affiliation: Department of Biochemistry and CARIM, University of Maastricht, 6229 ER Maastricht, The Netherlands.
authors.forename: Tilman
authors.initials: T
authors.lastname: Hackeng
authors.affiliation: Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Health Sciences Center, 6-155 Jackson Hall, 321 Church Street, Minneapolis, MN 55455, USA mayox001@umn.edu.
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Mayo
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002240:Carbohydrate Sequence; D005690:Galactose / Q000031:analogs & derivatives; D037502:Galectin 3 / Q000737:chemistry* / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008351:Mannans / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011499:Protein Processing, Post-Translational
chemical_list: D037502:Galectin 3; D008351:Mannans; C012990:galactomannan; D005690:Galactose
keywords: NMR; galactose; glycan; lectin; protein