FIGURE 1 | The Galectin family.

a | Galectins are a family of animal lectins characterized by conserved carbohydrate-recognition domains (CRDs) consisting of about 130 amino acids that are responsible for carbohydrate binding. So far, 15 mammalian galectins have been identified. They can be subdivided into three groups: those containing one CRD (galectin-1, 2, 5, 7, 10, 11, 13, 14 and 15); those containing two distinct CRDs in tandem, connected by a linker of up to 70 amino acids (galectin-4, 6, 8, 9 and 12); and galectin-3 (Gal-3), which consists of unusual tandem repeats of proline- and glycine-rich short stretches (a total of about 120 amino acids) fused onto the CRD. There are different isoforms of two-CRD type galectins, and these vary with respect to the length of the linker. b | Many galectins are either bivalent or multivalent with respect to their carbohydrate-binding activities: some one-CRD galectins exist as dimers; two-CRD galectins have two carbohydrate-binding sites; and galectin-3 forms oligomers when it binds to multivalent carbohydrates. Galectins can interact with cell-surface glycoconjugates, some of which are transmembrane proteins. Galectins can crosslink some of these glycoconjugates and trigger a cascade of transmembrane signalling events. Although binding to only two glycocoproteins is shown here, galectins can potentially cause the clustering of multiple multivalent glycoconjugates, resulting in a lattice formation. They can also bridge two cells of the same or different types, and bridge cells to extracellular matrix proteins. For simplicity, saccharides recognized by galectins are shown here as disaccharides, but they are likely to be oligosaccharides. In addition, the different colours of the saccharides shown here reflect the fact that different galectins bind to different sets of oligosaccharides.

Download file

If the slide opens in your browser, select "File > Save As" to save it.