Enzyme-linked (catalytic) receptors are transmembrane proteins that convert an extracellular chemical signal into intracellular catalytic activity: an extracellular ligand-binding domain and an intracellular enzymatic domain are joined in a single polypeptide, so ligand occupancy on one face of the membrane switches on enzyme function on the other. Receptor tyrosine kinases (RTKs), the largest and best-characterized class, transduce signals by a defined sequence — ligand binding drives association of two receptors into a cross-linked dimer, each monomer cross-phosphorylates tyrosine residues on its partner using phosphate donated by ATP, and the resulting phosphotyrosines act as docking platforms for cytoplasmic proteins bearing SH2 domains, permitting several signaling pathways to be initiated simultaneously and typically terminating in altered gene transcription. The concept belongs to cell biology and biochemistry within the study of signal transduction, explains how growth factors and certain hormones regulate cell growth, differentiation, and survival, and accounts for why constitutive activation of these receptors is a recurrent mechanism in oncogenesis.
Enzyme-linked (catalytic) receptors are transmembrane proteins that convert an extracellular chemical signal into intracellular catalytic activity: an extracellular ligand-binding domain and an intra…