Part I : Structures and
functions of animal lectins
Introduction to lectin families
This page provides a summary of the known lectin families, and an overview of the subcellular location and ligand binding specificities and evolution of the different families. The links below provide more detailed information on the structure, sugar-binding activity, biological function and evolution of proteins in each of the lectin families as well as annotated sequence alignments.
Complex oligosaccharide structures are displayed at cell surfaces, incorporated into the extracellular matrix and attached to secreted glycoproteins. These oligosaccharides can serve structural roles, mediate movement of glycoconjugates to the cell surface or act as markers that mediate cell-cell and cell-matrix recognition events. The non-structural roles of sugars generally require the participation of sugar-binding lectins (Drickamer and Taylor, 1998), in which sugar-binding activity can usually be ascribed to a single protein module within the lectin polypeptide. Such a module is referred to a carbohydrate-recognition domain (CRD).
CRDs in vertebrate lectins fall into a number of structurally distinct families. Of the eight well-established groups, four contain lectins that are predominantly intracellular and four contain lectins that generally function outside the cell. The intracellular lectins - calnexin family, M-type, L-type and P-type - are located in luminal compartments of the secretory pathway and function in the trafficking, sorting and targeting of maturing glycoproteins. The extracellular lectins - C-type, R-type, siglecs and galectins - are either secreted into the extracellular matrix or body fluids, or localized to the plasma membrane, and mediate a range of functions including cell adhesion, cell signalling, glycoprotein clearance and pathogen recognition. Recent findings point to the existence of additional new groups of animal lectins - F-box lectins, ficolins, chitinase-like lectins, F-type lectins and intelectins - some of which have roles complementary to those of the well-established lectin families.
- Information
- Calnexin M-type L-type P-type R-type Galectins I-type C-type
- F-box lectins Ficolins Chitinase-like lectins F-type Intelectins
- Sequence alignments
Adapted from Weis WI and Drickamer K (1994) Structure, 2:1227-40
