Galectins (also known as galaptins or S-lectin) are a family of proteins
defined by having at least one characteristic carbohydrate recognition domain
(CRD) with an affinity for β-galactosides and sharing certain sequence
elements. Members of the galectins family are found in mammals, birds,
amphibians, fish, nematodes, sponges, and some fungi. Galectins are known to
carry out intra- and extracellular functions through glycoconjugate-mediated
recogntion. From the cytosol they may be secreted by non-classical pathways,
but they may also be targeted to the nucleus or specific sub-cytosolic sites.
Within the same peptide chain some galectins have a CRD with only a few
additional amino acids, whereas others have two CRDs joined by a link peptide,
and one (galectin-3) has one CRD joined to a different type of domain [1,2,3].
The galectin carbohydrate recognition domain (CRD) is a β-sandwich of about
135 amino acid (see <PDB:1HLC>). The two sheets are slightly bent with 6
strands forming the concave side and 5 strands forming the convex side. The
concave side forms a groove in which carbohydrate is bound, and which is long
enough to hold about a linear tetrasaccharide [1,2,3,4,5].
A number of proteins are known to belong to this family:
Galectin-3 (also known as MAC-2 antigen; CBP-35 or IgE-binding protein), a
35 Kd lectin which binds immunoglobulin E and which is composed of two
domains: a N-terminal domain that consist of tandem repeats of a glycine/
proline-rich sequence and a C-terminal galectin domain.
Galectin-4 , which is composed of two galectin domains.
Galectin-7 , a keratinocyte protein which could be involved in cell-cell
and/or cell-matrix interactions necessary for normal growth control.
Galectin-8 , which is composed of two galectin domains.
Galectin-9 , which is composed of two galectin domains.
Human eosinophil lysophospholipase (EC 18.104.22.168)  (Charcot-Leyden crystal
protein), a protein that may have both an enzymatic and a lectin
activities. It forms hexagonal bipyramidal crystals in tissues and
secretions from sites of eosinophil-associated inflammation.
Caenorhabditis elegans 32 Kd lactose-binding lectin . This lectin is
composed of two galectin domains.
Caenorhabditis elegans lec-7 and lec-8.
The profile we developed covers the entire galectin domain.
March 2007 / Pattern removed, profile added and text revised.
PROSITE method (with tools and information) covered by this documentation:
Introduction to galectins.;
Trends Glycosci. Glycotechnol. 9:9-19(1997).
Leffler H., Carlsson S., Hedlund M., Qian Y., Poirier F.
PROSITE is copyright. It is produced by the SIB Swiss Institute
Bioinformatics. There are no restrictions on its use by non-profit
institutions as long as its content is in no way modified. Usage by and
for commercial entities requires a license agreement. For information
about the licensing scheme send an email to
or see: prosite_license.html.