Schematic representation of the structure of different members of the galectin family. Galectins can be subdivided into three groups: prototype galectins, which contain one carbohydrate recognition domain (CRD) and can form homodimers; tandem repeat-type galectins, which contain two distinct CRDs in tandem connected by a linker of up to 70 amino acids and are inherently bivalent; and the unique chimera-type galectin 3, which consists of unusual tandem repeats of proline- and glycine-rich short stretches fused onto the CRD. Following ligand binding, galectin 3 undergoes conformational changes, which enable its oligomerization into pentamers.