Fifth domain (immunoglobulin-like) of Trk receptor TrkB; member of the I-set of Ig superfamily (IgSF) domains
The members here are composed of the fifth domain of Trk receptor, TrkB, an immunoglobulin (Ig)-like domain which binds to neurotrophin. The Trk family of receptors are tyrosine kinase receptors, which mediate the trophic effects of the neurotrophin Nerve Growth Factor (NGF) family. Trks are activated by dimerization, leading to autophosphorylation of intracellular tyrosine residues, and triggering the signal transduction pathway. TrkB shares significant sequence homology and domain organization with TrkA and TrkC. The first three domains are leucine-rich domains while the fourth and fifth domains are Ig-like domains playing a part in ligand binding. TrKB is recognized by brain-derived neurotrophic factor (BDNF) and neurotrophin (NT)-4. In some cell systems NT-3 can activate TrkA and TrkB receptors. TrKB transcripts are found throughout multiple structures of the central and peripheral nervous systems. This group belongs to the I-set of IgSF domains