Epidermal growth factor ligand binding with

Trastuzumab is a recombinant DNA-derived, humanized monoclonal antibody that binds to the extracellular domain of the human epidermal growth factor receptor HER-2/ . This antibody blocks the natural ligand from binding and down-regulates the receptor. Trastuzumab is approved for the treatment of metastatic breast cancer in patients whose tumors overexpress HER-2/ . As a single agent it induces remission in about 15-20% of patients in combination with chemotherapy, it increases response rate and duration as well as 1-year survival. Trastuzumab is under investigation for other tumors that express HER-2... 

The insulin receptor is the prototype for a number of receptor enzymes with a similar structure and receptor Tyr kinase activity. The receptors for epidermal growth factor and platelet-derived growth factor, for example, have structural and sequence similarities to the insulin receptor, and both have a protein Tyr kinase activity that phosphorylates IRS-1. Many of these receptors dimerize after binding ligand the insulin receptor is already a dimer before insulin binds. The binding of adaptor proteins such as Grb2 to (P) Tyr residues is a common mechanism for promoting protein-protein interactions, a subject to which we return in Section 12.5. 

Fig. 6-24 Schematic representation of the epidermal growth factor (EGF) receptor. The receptor is an integral membrane protein with a single transmembrane domain. The ligand binding site is in the extracellular domain and there is a tyrosine kinase domain near the C terminus in the cytoplasm, (a) At rest the receptor exists as single subunits. (b) Upon binding EGF, the receptor forms dimers stabilized by noncovalent associations. After dimerization the activated tyrosine kinase phosphorylates tyrosine residues in the cytoplasmic domain prior to the recruitment of further proteins to bind to the receptor. The formation of a protein assembly on the cytoplasmic domain is necessary for activation of enzymes that regulate cell metabolism and gene transcription.

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