Intra- and inter-molecular interactions of human galectin-3: assessment by full-assignment-based NMR.
Related Articles Intra- and inter-molecular interactions of human galectin-3: assessment by full-assignment-based NMR.
Glycobiology. 2016 Feb 23;
Authors: Ippel H, Miller MC, Vértesy S, Zhang Y, Cañada FJ, Suylen D, Umemoto K, Romanò C, Hackeng T, Tai G, Leffler H, Kopitz J, André S, Kübler D, Jiménez-Barbero J, Oscarson S, Gabius HJ, Mayo KH
Abstract
Galectin-3 is an adhesion/growth-regulatory protein with a modular design comprising an N-terminal tail (NT, residues 1-111) and the conserved carbohydrate recognition domain (CRD, residues 112-250). The chimera-type galectin interacts with both glycan and peptide motifs. Complete (13)C/(15)N-assignment of the human protein makes NMR-based analysis of its structure beyond the CRD possible. Using two synthetic NT polypeptides covering residues 1-50 and 51-107, evidence for transient secondary structure was found with helical conformation from residues 5 to 15 as well as proline-mediated, multi-turn structure from residues 18 to 32 and around PGAYP repeats. Intramolecular interactions occur between the CRD F-face (the 5-stranded ?-sheet behind the canonical carbohydrate-binding 6-stranded ?-sheet of the S-face) and NT in full-length galectin-3, with the sequence P(23)GAW(26) … P(37)GASYPGAY(45) defining the primary binding epitope within the NT. Work with designed peptides indicates that the PGAX motif is crucial for self-interactions between NT/CRD. Phosphorylation at position Ser6 (and Ser12) (a physiological modification) and the influence of ligand binding have minimal effect on this interaction. Lastly, galectin-3 molecules can interact weakly with each other via the F-faces of their CRDs, an interaction that appears to be assisted by their NTs. Overall, our results add insight to defining binding sites on galectin-3 beyond the canonical contact area for ?-galactosides.
PMID: 26911284 [PubMed - as supplied by publisher]
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