Selectins structural homology

Figure 47-10. Schematic diagram of the structure of human L-selectin. The extracellular portion contains an amino terminal domain homologous to C-type lectins and an adjacent epidermal growth factor-like domain. These are followed by a variable number of complement regulatory-like modules (numbered circles) and a transmembrane sequence (blackdiamond). A short cytoplasmic sequence (open rectangle) is at the carboxyl terminal. The structures of P- and E-selectin are similar to that shown except that they contain more complement-regulatory modules.The numbers of amino acids in L-, P-, and E- selectins, as deduced from the cDNA sequences, are 385,789, and 589, respectively. (Reproduced, with permission, from Bevilacqua MP, Nelson RM Selectins. J Clin Invest 1993 91 370.)...

The term selectin was introduced to describe three adhesion molecules whose function and expression were highly selective and which possessed a terminal lectin domain. The nomenclature for each molecule relates to the cell on which they were first described E-selectin (endothelium), L-selectin (lymphocyte), and P-selectin (platelet). All three share similar structural features (1) an extracellular amino terminal carbohydrate-binding (i.e., lectin-like) domain that requires Ca2+ for activation (2) an epidermal growth factor-like domain and (3) repeated domains with homologies to complement-regulatoiy proteins. 

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