Recombinant Human Plexin B2 Protein, CF

Plexin B2 is a 240 kDa type I transmembrane (TM) glycoprotein of the Plexin B family of semaphorin receptors (1, 2). The human Plexin B2 cDNA encodes 1838 amino acids (aa) that include a 19 aa signal sequence, a 1178 aa extracellular domain (ECD), a 21 aa TM domain, and a 620 aa cytoplasmic region. The ECD contains one semaphorin domain (aa 20-466) and three IPT repeats (aa 803-1092). The ECD may be cleaved into two subunits, a 170 kDa alpha ‑chain (aa 20-1164) and an 80 kDa TM beta ‑chain, that remain noncovalently‑linked (1). Multiple splice variants may exist. Within aa 20-1160 in the ECD, human Plexin B2 shares 82%, 83%, 82% and 81% aa identity with mouse, rat, canine and bovine Plexin B2, respectively. The human B Plexins (B1, B2 and B3) share 39-47% aa identity with each other. Plexin B2 mRNA is expressed in proliferating cerebellar granule cell progenitors, neuroepithelium, developing neurons, growth plate chondrocytes, tooth bud inner enamel epithelium, glomeruli and mesenchyme of the developing kidney, and in germinal center B lymphocytes when T cell help is present (3-7). Plexin B2 is often co‑expressed with Plexin B1, and the two may form heterodimers (1, 4, 6). Genetic deletion of mouse Plexin B2 results in defects in proliferation and migration of cerebellar granule cells, abnormal development of the neural tube and disorganization of the embryonic brain; these defects are not seen when Plexin B1 is deleted (8, 9). Plexin B2 serves as a receptor for type 4 semaphorins, especially Sema4C (8-10). B Plexins, including Plexin B2, can bind the scatter factor receptors, Met and Ron, and activate them upon semaphorin engagement (1, 11).