Monovalent Interactions of Galectin-1

Abstract

Galectin-1, a β-galactoside binding lectin involved in immunoregulation and cancer, binds natural and many synthetic multivalent glycoconjugates with an apparent glycoside cluster effect, that is, affinity above and beyond what would be expected from the concentration of the determinant sugar. Here we have analyzed the mechanism of such cluster effects in solution at physiological concentration using a fluorescence anisotropy assay with a novel fluorescent high-affinity galectin-1 binding probe. The interaction of native dimeric and monomeric mutants of rat and human galectin-1 with mono- and divalent small molecules, fetuin, asialofetuin, and human serum glycoproteins was analyzed. Surprisingly, high-affinity binding did not depend much on the dimeric state of galectin-1 and thus is due mainly to monomeric interactions of a single carbohydrate recognition domain. The mechanism for this is unknown, but one possibility includes additional interactions that high-affinity ligands make with an extended binding site on the carbohydrate recognition domain. It follows that such weak additional interactions must be important for the biological function of galectin-1 and also for the design of galectin-1 inhibitors.

The Involvement of CD146 and Its Novel Ligand Galectin-1 in Apoptotic Regulation of Endothelial Cells

“…Many of the proposed regulatory effects of Galectin-1 appeared to involve reversible binding to receptors with affinities in the low M range (42)(43)(44)(45). In addition, Galectin-1 exhibits unique biochemical properties, which make its functional analysis even more complex.…”

“…Thus, glycan recognition partially protects Galectin-1 from oxidative inactivation and enhances Galectin-1 dimerization (46). Indeed, Galectin-1 exists as a mixture of monomers and dimers at physiological concentrations (45,47). Therefore, the different functions of this lectin can be due to 1) the monomeric or dimeric form of this protein (45,(47)(48)(49)(50), 2) the influence of oxidative versus reducing microenvironments (46), 3) the engagement of Galectin-1 with ligands (51), and 4) the in vivo levels of Galectin-1 in physiological and pathological concentrations.…”

Synthesis of 1,2,3-triazole-linked galactohybrids and their inhibitory activities on galectins

“…42 Galectin-1 was produced, purified and tested at about 0.5 µM with a thiodigalactoside amide probe (tdga-probe, 0.1 µM) as previously reported. 41 …”

“…Finally, the axial position of HO-C(4) and the equatorial position of H-C(4) in both anomers was proved by 3 The binding affinities of galectin-1 and -3 for selected compounds 17 were estimated by a fluorescent anisotropy assay. 40,41,42 Compounds depicted in Table 3 were tested up to 5 mM concentrations and gave K d values in the range of 1-4 mM, except trisaccharide 17j. The latter exhibited enhanced galectin-3 binding with K d 50 μM and 160-fold preference for galectin-3.…”

Molecular mimicry of conformationally diverse β-sheets by using α/β-peptide foldamers

“…[129][130][131] The major secondary structure of gal-1 is also -sheet, and folds into a -sandwich structure that forms homodimers in solution with dimerization KD of 1-7 M. [132][133] Anginex treatment in gal-1 null mice did not result in tumor suppression, which highlighted the importance of gal-1 in anti-angiogenic effect of anginex.…”