Galectins are a family of β-galactoside-binding proteins that mediate in a broad variety of physiological functions as result of their interaction with carbohydrates, participating in cell-cell interactions, immune response, and intracellular signaling, among others.
Human galectin-4 (hGal-4) is a tandem-repeat protein with two carbohydrate recognition domains (CRD) united through a linker-peptide. This lectin is mainly expressed in healthy epithelial cells of the intestinal tract, playing a crucial role on the stabilization of lipid rafts and participating in apical trafficking. Both up- and down-regulation of hGal-4 expression levels have been found in cancerous tissues, marking this lectin an interesting drug target.
The relevance of the molecular recognition of human blood group antigens by hGal-4 in biological processes has been already reported. However, the essential features of the interaction event, including the knowledge of the dynamic properties of both the receptor and the ligand are yet to be ascertained.
To gain insight into the key elements of the recognition process, the interaction between hGal4 CRD1 and the blood group A- and B-antigens have been studied by NMR from the ligand and receptor’s perspectives. In particular, the analysis of STD-NMR, tr-NOESY and HSQC experiments have permitted shedding light into the fine details of the glycan-lectin interaction.
Finally, the combination of the NMR experimental data with those deduced from computational protocols have allowed explaining the selectivity of the lectin towards the distinct ligands.
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