Structure
Most RTKs are single subunit receptors but some exist as multimeric complexes, e.g., the insulin receptor that forms disulfide-linked dimers in the absence of hormone; moreover, ligand binding to the extracellular domain induces formation of receptor dimers. Each monomer has a single hydrophobic transmembrane-spanning domain composed of 25-38 amino acids, an extracellular N-terminal region, and an intracellular C-terminal region. The extracellular N-terminal region exhibits a variety of conserved elements including immunoglobulin (Ig)-like or epidermal growth factor (EGF)-like domains, fibronectin type III repeats, or cysteine-rich regions that are characteristic for each subfamily of RTKs; these domains contain primarily a ligand-binding site, which binds extracellular ligands, e.g., a particular growth factor or hormone. The intracellular C-terminal region displays the highest level of conservation and comprises catalytic domains responsible for the kinase activity of these receptors, which catalyses receptor autophosphorylation and tyrosine phosphorylation of RTK substrates.
Read more about this topic: Receptor Tyrosine Kinases
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