|PROSITE documentation PDOC00537 [for PROSITE entry PS50041]|
A number of different families of proteins share a conserved domain which was first characterized in some animal lectins and which seem to function as a calcium-dependent carbohydrate-recognition domain [1,2,3]. This domain, which is known as the C-type lectin domain (CTL) or as the carbohydrate-recognition domain (CRD), consists of about 110 to 130 residues. There are four cysteines which are perfectly conserved and involved in two disulfide bonds. A schematic representation of the CTL domain is shown below.
+------+ | | xcxxxxcxxxxxxxCxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxCxxxxWxCxxxxCx | | | ************|* +----+ +-------------------------------------------------+
'C': conserved cysteine involved in a disulfide bond. 'c': optional cysteine involved in a disulfide bond. '*': position of the pattern.
The categories of proteins, in which the CTL domain has been found, are listed below.
Type-II membrane proteins where the CTL domain is located at the C-terminal extremity of the proteins:
Proteins that consist of an N-terminal collagenous domain followed by a CTL-domain , these proteins are sometimes called 'collectins':
Selectins (or LEC-CAM) [6,7]. Selectins are cell adhesion molecules implicated in the interaction of leukocytes with platelets or vascular endothelium. Structurally, selectins consist of a long extracellular domain, followed by a transmembrane region and a short cytoplasmic domain. The extracellular domain is itself composed of a CTL-domain, followed by an EGF-like domain and a variable number of SCR/Sushi repeats. Known selectins are:
Large proteoglycans that contain a CTL-domain followed by one copy of a SCR/ Sushi repeat, in their C-terminal section:
In addition to the CTL and Sushi domains, these proteins also contain, in their N-terminal domain, an Ig-like V-type region, two or four link domains (see <PDOC00955>) and up to two EGF-like repeats.
Two type-I membrane proteins:
Various other proteins that uniquely consist of a CTL domain:
As a signature pattern for this domain, we selected the C-terminal region with its three conserved cysteines.Note:
All CTL domains have five Trp residues before the second Cys, with the exception of tunicate lectin and cockroach LPS-BP which have Leu.Expert(s) to contact by email:
April 2006 / Pattern revised.
PROSITE methods (with tools and information) covered by this documentation:
|Title||Two distinct classes of carbohydrate-recognition domains in animal lectins.|
|Source||J. Biol. Chem. 263:9557-9560(1988).|
|Title||Evolution of Ca(2+)-dependent animal lectins.|
|Source||Prog. Nucleic Acid Res. Mol. Biol. 45:207-232(1993).|
|Source||Curr. Opin. Struct. Biol. 3:393-400(1993).|
|Title||The asialoglycoprotein receptor: a model for endocytic transport receptors.|
|5||Authors||Weis W.I. Kahn R. Fourme R. Drickamer K. Hendrickson W.A.|
|Title||Structure of the calcium-dependent lectin domain from a rat mannose-binding protein determined by MAD phasing.|
|Title||Sweetening the selectin pot.|
|Source||Curr. Biol. 1:125-128(1991).|
|Title||Selectins: interpreters of cell-specific carbohydrate information during inflammation.|
|8||Authors||Jomori T. Natori S.|
|Title||Molecular cloning of cDNA for lipopolysaccharide-binding protein from the hemolymph of the American cockroach, Periplaneta americana. Similarity of the protein with animal lectins and its acute phase expression.|
|Source||J. Biol. Chem. 266:13318-13323(1991).|
|9||Authors||Ng N.F.L. Hew C.-L.|
|Title||Structure of an antifreeze polypeptide from the sea raven. Disulfide bonds and similarity to lectin-binding proteins.|
|Source||J. Biol. Chem. 267:16069-16075(1992).|