title: Stimulation of tyrosine-specific phosphorylation in vitro by insulin-like growth factor I.
abstract: Several mitogens elicit tyrosine-specific protein kinase activities. Although the physiological significance of this is unclear, the generality of these reactions implies that this may be an inherent feature of growth factor-growth factor receptor interactions. The observed mitogenic properties of the polypeptide insulin-like growth factor I (IGF-I) indicated that it might also stimulate such activity. We report here that IGF-I stimulates a tyrosine-specific protein kinase in a time- and dose-dependent fashion. The close correspondence between an approximate 50% effective dose (ED50) of phosphorylation and an approximate Kd for IGF-I binding leads us to conclude that a high-affinity IGF-I receptor, not the structurally similar insulin receptor, is the mediator of IGF-I stimulated kinase activity. Immunoprecipitation indicates that both the beta-subunit of the IGF-I receptor and the beta-subunit of the insulin receptor are targets for the IGF-I-stimulated protein kinase.
mesh_terms: D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D046911:Macromolecular Substances; D008970:Molecular Weight; D010455:Peptides / Q000494:pharmacology*; D010766:Phosphorylation; D010920:Placenta; D011247:Pregnancy; D011494:Protein Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000494:pharmacology*
chemical_list: D007328:Insulin; D046911:Macromolecular Substances; D010455:Peptides; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin