C-type Lectins

C-type lectins are CA-dependent glycan-binding proteins that share primary and secondary structural homology in their carbohydrate-recognition domains (CRDs). These proteins have a C-type lectin fold, which is a fold with highly variable protein sequence that is also present in many proteins that do not bind carbohydrates (C-type lectin domain [CTLD]-containing proteins). C-type lectins and proteins with CTLDs are found in all organisms. The large family of C-type lectins includes collectins, selectins, endocytic receptors, and proteoglycans. Some of these proteins are secreted and others are transmembrane proteins. They often oligomerize into homodimers, homotrimers, and higher-ordered oligomers, which increases their avidity for multivalent ligands. Although they share structural homology, C-type lectins usually differ significantly in the types of glycans that they recognize with high affinity. These proteins function as adhesion and signaling receptors in many immune functions such as inflammation and immunity to tumor and virally infected cells.