UMMS Affiliation
Department of Pathology; Program in Molecular Medicine
Publication Date
1992-05-01
Document Type
Article
Subjects
3T3 Cells; Adenosine Triphosphate; Animals; *Cell Transformation, Neoplastic; Chickens; Immune Sera; Kinetics; Mice; Phosphorylation; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; *Proto-Oncogenes; Receptor, Epidermal Growth Factor; Recombinant Fusion Proteins; Substrate Specificity
Disciplines
Life Sciences | Medicine and Health Sciences
Abstract
We have compared the protein tyrosine kinase activities of the chicken epidermal growth factor receptor (chEGFR) and three ErbB proteins to learn whether cancer-activating mutations affect the kinetics of kinase activity. In immune complex assays performed in the presence of 15 mM Mn2+, ErbB proteins and the chEGFR exhibited highly reproducible tyrosine kinase activity. Under these conditions, the ErbB and chEGFR proteins had similar apparent Km [Km(app)] values for ATP. The ErbB proteins appeared to be activated, as they had at least 3-fold-higher relative Vmax(app) for autophosphorylation and approximately 2-fold higher relative Vmax(app) for the phosphorylation of the exogenous substrate TK6 (a bacterially expressed fusion protein containing the C-terminal domain of the human EGFR). The ErbB kinases had both higher Km(app) and higher Vmax(app) for the phosphorylation of the exogenous substrate TK6 than did the chEGFR. The ratios of the Vmax(app) to the Km(app) for TK6 phosphorylation suggested that the ErbB proteins had lower catalytic efficiencies for the exogenous substrate than did the chEGFR. The three tested ErbB proteins had cytoplasmic domain mutations that conferred distinctive disease potentials. These mutations did not affect the kinetics for the phosphorylation of the exogenous substrate TK6. Two of the ErbB proteins contained all of the sites used for autophosphorylation. In these, a mutation that broadened oncogenic potential to endothelial cells caused an additional increase in Vmax(app) for autophosphorylation. Thus, mutations that change the EGFR into an ErbB oncogene cause multiple changes in the kinetics of protein tyrosine kinase activity.
Source
Mol Cell Biol. 1992 May;12(5):2010-6.
Journal/Book/Conference Title
Molecular and cellular biology
Related Resources
PubMed ID
1314948
Repository Citation
Nair N, Davis RJ, Robinson HL. (1992). Protein tyrosine kinase activities of the epidermal growth factor receptor and ErbB proteins: correlation of oncogenic activation with altered kinetics. Open Access Articles. Retrieved from https://escholarship.umassmed.edu/oapubs/1463