<p>This entry represents the plexin repeat, which is a disulphide-rich motif with an alpha+beta core structure that contains two conserved disulphides. This repeat motif is found in several different extracellular receptors, including plexins, which are involved in the development of neural and epithelial tissues [<cite idref="PUB00042651"/>]; in semaphorins, which regulate axon guidance, immune function and angiogenesis [<cite idref="PUB00015415"/>]; in integrins, which are important Metazoan adhesion receptors that transmit conformational change bidirectionally across the membrane (integrin alpha and beta subunits form a head and two long legs in the ectodomain and span the membrane) [<cite idref="PUB00037805"/>]; and in hepatocyte growth factor receptor, which plays important roles in normal development and in tumour growth and metastasis [<cite idref="PUB00015416"/>].</p>