title: Characterization of the activity of human MAP kinase-interacting kinase Mnk1b.
abstract: Human mitogen-activated protein (MAP) kinase interacting kinase 1b (Mnk1b) is a splice variant of human Mnk1a, which has been identified in our laboratory [A. O'Loghlen, V.M. Gonzalez, D. Pineiro, M.I. Perez-Morgado, M. Salinas, M.E. Martin, Identification and molecular characterization of Mnk1b, a splice variant of human MAP kinase-interacting kinase Mnk1, Exp. Cell Res. 299 (2004) 343-355]. Mnk1b has much higher basal eIF4E kinase activity than Mnk1a. Because Mnk1b presents different features in its C-terminus with respect to Mnk1a, we have studied in this paper the potential role of these structural differences in determining the higher basal eIF4E kinase activity as well as the subcellular localization of Mnk1b. In this paper, we demonstrate that phosphorylation of the Thr209 and Thr214 in the activation loop of Mnk1b is necessary for its activation. However, the different kinase activity between Mnk1a and Mnk1b is independent of the phosphorylation status of the activation loop residues. By deletion of the C-terminal tail in Mnk1a, we confirmed that the absence of this sequence is not responsible for the higher eIF4E kinase activity present in Mnk1b. Moreover, our findings support a crucial role of the 12 amino acids, particularly the Ala344, in the C-terminal specific region of Mnk1b (Mnk1bSR), on the kinase activity of the protein.
authors.affiliation: Servicio de Bioquímica-Investigación, Hospital Ramón y Cajal, Ctra. Colmenar km. 9,100. E-28034 Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: O'Loghlen
authors.forename: Víctor M
authors.initials: VM
authors.lastname: González
authors.forename: Teresa
authors.initials: T
authors.lastname: Jurado
authors.forename: Matilde
authors.initials: M
authors.lastname: Salinas
authors.forename: M Elena
authors.initials: ME
authors.lastname: Martín
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001665:Binding Sites; D020134:Catalytic Domain; D002460:Cell Line; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism*; D019793:Fluorescein; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000166:cytology; D019950:Mitogen-Activated Protein Kinase 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals; D010766:Phosphorylation; D010957:Plasmids; D011485:Protein Binding; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D039561:Eukaryotic Initiation Factor-4E; D005456:Fluorescent Dyes; D047908:Intracellular Signaling Peptides and Proteins; D019913:Nuclear Localization Signals; D020033:Protein Isoforms; C491395:MKNK1 protein, human; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D019793:Fluorescein