Selectins binding specificity

Proteins termed selectins are members of the C-type family. Selectins bind immune-system cells to the sites of injury in the inflammatory response (Figure 11.30). The L, E, and P forms of selectins bind specifically to carbohydrates on /ymph-node vessels, endothelium, or activated blood platelets, respectively. New therapeutic agents that control inflammation may emerge from a deeper understanding of how selectins bind and distinguish different carbohydrates. 

At least three other families of plasma membrane proteins are also involved in surface adhesion (Fig. 11-22). Cadherins undergo homophilic ( with same kind ) interactions with identical cadherins in an adjacent cell. Immunoglobulin-like proteins can undergo either homophilic interactions with their identical counterparts on another cell or heterophilic interactions with an integrin on a neighboring cell. Selectins have extracellular domains that, in the presence of Ca2+, bind specific polysaccharides on the surface of an adjacent cell. Selectins are present primarily in the various types of blood cells and in the endothelial cells that line blood vessels (see Fig. 7-33). They are an essential part of the blood-clotting process. 

Figure 11.30. Selectius Mediate Cell-Cell luteractious. The scanning electron micrograph shows lymphocytes adhering to the endothelial lining of a lymph node. The L selectins on the lymphocyte surface bind specifically to carbohydrates on the lining of the lymph-node vessels. [Courtesy of Dr. Eugene Butcher.]...

Revelle, B M, Scott, D, Beck, P J, Single amino acid residues in the E- and P-selectin epidermal growth factor domains can determine carbohydrate binding specificity, J. Biol Chem., 271, 16160-16170, 1996. 

Distribution and binding specificity of selectins (for references see the text)... 

Ligand binding by the selectins illustrates another mechanism by which binding specificity can be achieved. In this case, binding to 3 -sialyl-Lewis and related sugars occurs through additional interactions between the CRD and multiple saccharide moieties of the ligand [15—17],... 

---