Fig. 1

Structure of prototype of receptor tyrosine kinase and mechanism of activation. Receptor tyrosine kinases (RTKs) have the following structural segments from N- to C-terminal: immunoglobulin folds, transmembrane region, juxtamembrane region, N-lobe, activation loop, C-lobe and cytoplasmic tail. RTKs reside at the plasma membrane as a monomer. Ligand binding crosslinks receptor molecules and induces conformational changes that lead to receptor autophosphorylation and activation. Phosphorylated RTK either serves as a docking site for adaptor proteins (B) or may directly phosphorylate signaling molecules (A). Adaptor proteins or signaling molecules bind to phosphorylated receptor through Src homology 2 (SH2) or phosphotyrosine-binding (PTB) domain. Docked adaptor proteins further transduce signal by phosphorylating other downstream molecules (C, D)