title: Molecular size of the epidermal growth factor receptor-kinase as determined by radiation inactivation.
abstract: Radiation inactivation with high energy electrons from a linear accelerator was used to determine the functional molecular size of the epidermal growth factor (EGF) binding site and the tyrosine-specific protein kinase activity in A-431 membranes. The target size of the protein portion of the EGF receptor glycoprotein was 147,000 daltons when the radiation-dependent decrease in maximal binding capacity was measured. Since the target size is in good agreement with the molecular size of the protein portion of the EGF receptor determined by denaturing biochemical methods, it appears that the monomeric receptor is the functional binding site in situ. The target size of the EGF-stimulated kinase activity associated with the affinity-purified EGF receptor/kinase was 133,000 and 144,000 daltons when assayed for the ability to autophosphorylate or to phosphorylate a tyrosine-containing peptide, respectively. However, the target size of the kinase activity that did not adhere to an EGF-affinity column was 54,000 and 69,000 daltons when assayed for phosphorylation of endogenous and exogenous substrates, respectively. Intermediate target sizes were obtained when kinase assays were performed on membranes prior to fractionation by affinity chromatography. These results, taken with other biochemical data, indicate that A-431 membranes contain a kinase activity that is a domain of the glycoprotein that contains the EGF binding site and that the membranes also contain another tyrosine-specific kinase or kinases that have an average size of approximately 60,000 daltons.
authors.forename: H T
authors.initials: HT
authors.lastname: Haigler
authors.forename: D
authors.initials: D
authors.lastname: End
authors.forename: E
authors.initials: E
authors.lastname: Kempner
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000032:analysis; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors; D006801:Humans; D051379:Mice; D008970:Molecular Weight; D009369:Neoplasms; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism / Q000528:radiation effects*; D011505:Protein-Tyrosine Kinases; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; D011494:Protein Kinases; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases