Background information
Semaphorins are a family of cell surface and secreted proteins that are conserved from insects to humans. Members of this family of proteins are approximately 750 amino acids in length (including signal sequences) and are defined by a conserved extracellular “semaphorin†domain of approximately 500 amino acids containing 14-16 cysteines, blocks of conserved sequences and no obvious repeats. The transmembrane semaphorins are characterized by an additional 80 amino acid transmembrane domain and an 80-110 amino acid cytoplasmic domain. Secreted and cell-bound semaphorins chemically attract and repel the growth of neural axons, guiding the development of intricate networks of neural tissue. SEMA4B (semaphorin-4B), also known as SemC or SEMAC, is an 832 amino acid single-pass type I membrane protein that belongs to the semaphorin family and exists as two alternatively spliced isoforms. Containing one Ig-like C2-type (immunoglobulin-like) domain, a PSI domain and a single sema domain, SEMA4B is encoded by a gene located on human chromosome 15.
