Structural Insights Into Galectin-3 Recognition of a Selenoglycomimetic.

Chimera-type galectin-3 (Gal-3) is a β-galactoside-binding protein containing a single conserved carbohydrate-recognition domain, crucial in fibrosis and carcinogenesis. Selenium-based Gal-3 inhibitors have emerged as promising therapeutic agents, particularly for treating neoplastic diseases. Among them, a seleno-digalactoside (SeDG) substituted with a benzyl group at position 3 of both saccharide residues (benzyl 3,3'-seleno-digalactoside, SeDG-Bn), attracted considerable attention for its selectivity and potent inhibitory efficacy against Gal-3. NMR spectroscopy and molecular dynamics simulations were combined to investigate the binding of SeDG-Bn to Gal-3 at the molecular level. This approach revealed the recognized epitope, the binding mode within Gal-3 binding pocket and enabled the generation of a 3D model of the complex. Our findings show that the presence of a single benzyl group establishes hydrophobic contacts with amino acids in Gal-3 β-sheets S2 and S3, crucially enhancing the binding affinity compared to unmodified SeDG. The digalactose backbone orientation in Gal-3 binding site is partially modified by the benzyl group with respect to complexes with lactosamine and SeDG. These results provide valuable insights into the design of more potent and selective inhibitors for Gal-3, potentially contributing to new therapeutic strategies for conditions such as cancer and fibrosis.