title: MAP kinases from bovine brain: purification and characterization.
abstract: We have purified 42- and 44-kilodalton (kDa) isoforms of the mitogen-activated protein (MAP) kinase family from bovine brain. The kinases were assayed with myelin basic protein as the substrate and detected by anti-sea star p44mpk antibody. Purification was achieved using phenyl-Sepharose, polylysine-agarose, hydroxylapatite, and Mono-Q column chromatography. Both myelin basic protein and smooth muscle caldesmon, but not histone H1, served as good substrates. Based on chromatographic behaviors and specific activities toward myelin basic protein, it is likely that the 42-kDa brain isoform is similar to that of brain tau kinase. The 44-kDa enzyme, however, is a novel brain MAP kinase isoform not reported previously. Although it has been demonstrated that p44mpk can be activated in vitro through phosphorylation by the tyrosine kinase p56lck, neither of the brain kinases were significantly stimulated by the tyrosine kinases p56lck, p56lyn, or p59fyn. However, based on antibody cross-reactivity, a MAP kinase kinase is present in the crude brain extract. Both brain MAP kinases were capable of autophosphorylation which occurred, at least in part, on tyrosine residues. However, only the 44-kDa isoform showed a significant degree of coincident activation.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, ON, Canada.
authors.forename: T J
authors.initials: TJ
authors.lastname: Childs
authors.forename: A S
authors.initials: AS
authors.lastname: Mak
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002417:Cattle; D002454:Cell Differentiation; D003429:Cross Reactions; D004789:Enzyme Activation; D007527:Isoenzymes / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D011494:Protein Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D013379:Substrate Specificity; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D002148:Calmodulin-Binding Proteins; D007527:Isoenzymes; D004676:Myelin Basic Protein; D019000:Phosphotyrosine; D014443:Tyrosine; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases