Figure 3.

Regulation of galectin activity. Several galectins require reduced thiol groups to maintain carbohydrate recognition activity. Formation of intra- and inter-molecular disulfide bridges can result in significant conformational changes the preclude carbohydrate recognition. As monomers appear to be a key intermediate in oxidative inactivation and carbohydrates can drive dimerization, ligand appears to reduce oxidative inactivation by facilitating dimer formation (${\text{K}}_{\text{d}}^1$ < ${\text{K}}_{\text{d}}^2$). [hi] = higher concentrations of galectin-1 (Gal-1). [low] = lower concentrations of Gal-1. In contrast, several galectins, especially tandem repeat and chimeric galectins, rely on linker peptide bound carbohydrate recognition domains or N terminal collagen-like domains to facilitate dimerization. Cleavage of intervening peptides that connect oligomerization domains to functional carbohydrate recognition domains can render carbohydrate recognition domains monomeric and therefore incapable of generating signaling lattices typically thought to be required for optimal galectin-mediated signaling.