Receptor Tyrosine Kinase | RTK Signalling

Receptor tyrosine kinases (RTKs) are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 59 encode receptor tyrosine kinase proteins. Most RTKs are single subunit receptors but some exist as multimeric complexes, e.g., the insulin receptor that forms disulfide linked dimers in the presence of hormone (insulin); moreover, ligand binding to the extracellular domain induces formation of receptor dimers.[6] Each monomer has a single hydrophobic transmembrane-spanning domain composed of 25 to 38 amino acids, an extracellular N terminal region, and an intracellular C terminal region. In biochemistry, a kinase is a type of enzyme that transfers phosphate groups (see below) from high-energy donor molecules, such as ATP (see below) to specific target molecules (substrates); the process is termed phosphorylation. The opposite, an enzyme that removes phosphate groups from targets, is known