STRUCTURE AND FUNCTION OF SH2 DOMAINS

In order for cells to respond to their environment, a series of regula ted molecular events has to take place. External signalling molecules bind to cellular receptors and thereby trigger the activation of multi ple intracellular pathways, which modify cellular phenotypes. The cell -surface receptors for a wide range of polypeptide hormones possess pr otein tyrosine kinase activity, which is induced by binding of the app ropriate extracellular ligand. Tyrosine phosphorylation can act as a m olecular switch, by initiating the recruitment of cytoplasmic effector molecules containing Src homology (SH) 2 domains, to activated recept ors. These SH2-containing proteins, in turn, regulate intracellular si gnalling pathways. Here, we discuss the role of tyrosine phosphorylati on in triggering signalling pathways, as well as the functions of SH2 domains, which mediate these events through phosphotyrosine-dependent protein-protein interactions.