title: Regulatory mechanism of Ca2+/calmodulin-dependent protein kinase kinase.
abstract: Ca(2+)/calmodulin-dependent protein kinase kinase (CaM-KK) is a novel member of the CaM kinase family, which specifically phosphorylates and activates CaM kinase I and IV. In this study, we characterized the CaM-binding peptide of alphaCaM-KK (residues 438-463), which suppressed the activity of constitutively active CaM-KK (84-434) in the absence of Ca(2+)/CaM but competitively with ATP. Truncation and site-directed mutagenesis of the CaM-binding region in CaM-KK reveal that Ile(441) is essential for autoinhibition of CaM-KK. Furthermore, CaM-KK chimera mutants containing the CaM-binding sequence of either myosin light chain kinases or CaM kinase II located C-terminal of Leu(440), exhibited enhanced Ca(2+)/CaM-independent activity (60% of total activity). Although the CaM-binding domains of myosin light chain kinases and CaM kinase II bind to the N- and C-terminal domains of CaM in the opposite orientation to CaM-KK (Osawa, M., Tokumitsu, H., Swindells, M. B., Kurihara, H., Orita, M., Shibanuma, T., Furuya, T., and Ikura, M. (1999) Nat. Struct. Biol. 6, 819-824), the chimeric CaM-KKs containing Ile(441) remained Ca(2+)/CaM-dependent. This result demonstrates that the orientation of the CaM binding is not critical for relief of CaM-KK autoinhibition. However, the requirement of Ile(441) for autoinhibition, which is located at the -3 position from the N-terminal anchoring residue (Trp(444)) to CaM, accounts for the opposite orientation of CaM binding of CaM-KK compared with other CaM kinases.
authors.affiliation: Department of Chemistry, Kagawa Medical University, 1750-1 Miki-cho, Kita-gun, Kagawa 761-93, Japan. tokumit@kms.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Tokumitsu
authors.forename: M a
authors.initials: Ma
authors.lastname: Muramatsu
authors.forename: M
authors.initials: M
authors.lastname: Ikura
authors.forename: R
authors.initials: R
authors.lastname: Kobayashi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D002384:Catalysis; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D015723:Gene Library; D007532:Isoleucine / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection
chemical_list: D018076:DNA, Complementary; D010455:Peptides; D011994:Recombinant Proteins; D007532:Isoleucine; D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase