title: Expression, purification and characterization of recombinant mitogen-activated protein kinase kinases.
abstract: Mitogen-activated protein (MAP) kinase kinases (MKKs) are dual-specificity protein kinases which activate p42mapk and p44mapk by phosphorylation of regulatory tyrosine and threonine residues. cDNAs for two isotypes of MKK, MKK1 and MKK2, have been isolated from several species. Here we describe construction of recombinant baculoviruses for high-level expression of histidine-tagged rat MKK1 and MKK2, and procedures for production of nearly homogeneous MKK1 and MKK2 fusion proteins, in both inactive and active forms. Co-infection of Sf9 cells with either MKK1 or MKK2 virus together with recombinant viruses for Raf-1, pp60src (Y527F) and c-Ha-Ras resulted in activations of 250-fold and 150-fold for MKK1 and MKK2 respectively. Specific activities towards kinase-defective p42mapk were of the order of several hundred nanomoles of phosphate transferred/min per mg of MKK protein. The Michaelis constants for both enzymes were approx. 1 microM. Preparations of activated MKK were apparently free of Raf-1 as assessed by Western blotting. Raf-1 phosphorylated MKK1 on one major tryptic phosphopeptide, the phosphorylation of which increased with time. This phosphopeptide contained only phosphoserine and possessed neutral overall charge at pH 1.9 on two-dimensional peptide mapping. Phosphorylation of MKK1 by Raf-1 correlated with activation and reached a plateau of approximately 2 mol/mol.
authors.affiliation: Howard Hughes Medical Institute Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.
authors.forename: P
authors.initials: P
authors.lastname: Dent
authors.forename: Y H
authors.initials: YH
authors.lastname: Chow
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: D K
authors.initials: DK
authors.lastname: Morrison
authors.forename: R
authors.initials: R
authors.lastname: Jove
authors.forename: T W
authors.initials: TW
authors.lastname: Sturgill
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D006639:Histidine; D007527:Isoenzymes / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000096:biosynthesis* / Q000302:isolation & purification* / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D018411:Spodoptera; D014162:Transfection
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D006639:Histidine; D011494:Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases