title: Effect of carboxyl terminal truncation on the tyrosine kinase activity of the epidermal growth factor receptor.
abstract: The carboxyl terminal domain of the epidermal growth factor receptor (EGFR) is an important regulatory region in mediating the tyrosine kinase-dependent biological effects of EGF. The effect of a 164-amino-acid carboxyl deletion of the EGFR or the EGFR cytoplasmic kinase domain on in vitro tyrosine kinase activity was assessed. C'-terminal truncation of the EGFR resulted in dependence on Mn2+ for full activity. The EGFR kinase domain (kd EGFR) and the C'-terminally truncated kinase domain (kd c'1022 EGFR) also exhibited a strong preference for Mn2+ compared to Mg2+, with kd c'1022 EGFR being completely inactive in the presence of Mg2+ alone. Sphingosine or ammonium sulfate specifically activated both kd EGFR and kd c'1022 EGFR. EGFR and c'1022 EGFR displayed similar EGF-stimulated in vitro tyrosine kinase activities; however, kd EGFR was 5- to 10-fold more active in vitro than kd c'1022 EGFR. Thus, the regulatory contribution of the C'-terminus is most evident when the EGFR ligand binding domain is removed. These results indicate that an intact EGFR C'-terminus is necessary for the protein to assume a fully active conformation.
authors.affiliation: Department of Chemistry, University of California, San Diego, La Jolla 92093-0650.
authors.forename: P B
authors.initials: PB
authors.lastname: Wedegaertner
authors.forename: G N
authors.initials: GN
authors.lastname: Gill
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D002460:Cell Line; D066246:ErbB Receptors / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D005822:Genetic Vectors; D006801:Humans; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology
chemical_list: D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases