title: Autophosphorylation-activated protein kinase inactivates the protein tyrosine phosphatase activity of protein phosphatase 2A.
abstract: Phosphorylation of the catalytic subunit of protein phosphatase 2A (PP2A) on threonines with a distinct autophosphorylation-activated protein kinase [Guo and Damuni (1993) Proc. Natl. Acad. Sci. USA 90, 2500-2504] inactivated the phosphatase with 32P-labelled myelin basic protein prepared by incubation with the kinase domain of the epidermal growth factor receptor, the src-family protein kinases p56lck and p60c-src, myelin basic protein kinase-1, or protamine kinase. Phosphoamino acid analysis demonstrated that the kinase domain of the epidermal growth factor receptor, p56lck and p60c-src phosphorylated myelin basic protein on tyrosines, that the protamine kinase phosphorylated myelin basic protein on serines, and that myelin basic protein kinase-1 phosphorylated myelin basic protein on threonines. The results demonstrate that the autophosphorylation-activated protein kinase not only inactivates the protein serine/threonine phosphatase, but also the protein tyrosine phosphatase activity of PP2A. This autophosphorylation-activated protein kinase-mediated inactivation of PP2A may, in response to extracellular stimuli, not only contribute to the enhanced phosphorylation of cellular proteins on serines and threonines but also on tyrosines.
authors.affiliation: Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey 17033.
authors.forename: Z
authors.initials: Z
authors.lastname: Damuni
authors.forename: H
authors.initials: H
authors.lastname: Xiong
authors.forename: M
authors.initials: M
authors.lastname: Li
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3; D007700:Kinetics; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D019000:Phosphotyrosine; D006656:Protamine Kinase / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D010761:Phosphorus Radioisotopes; D011994:Recombinant Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D016392:Proto-Oncogene Proteins pp60(c-src); D006656:Protamine Kinase; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases