Enzymatic characteristics of a Ser/Thr protein kinase, SpkA, from Myxococcus xanthus.
Two Ser/Thr protein kinases, SpkA and SpkB, selected from Myxococcus xanthus based on amino acid sequence similarities with the catalytic subunits of cAMP-dependent protein kinases (PKA) were synthesized using a cell-free protein synthesis system. In various protein kinase assays, purified StkA and StkB showed their highest protein kinase activities in a PKA assay using the selective PKA substrate Kemptide and in a protein kinase C (PKC) assay using the selective PKC substrate neurogranin((28-43)), respectively. SpkA had apparent K(m) values of 45 microM and 37 microM for Kemptide and ATP, respectively. Phosphorylation of Kemptide was inhibited by a specific PKA inhibitor peptide, PKI(5-24), and the IC(50) and K(i) values for inhibition of the SpkA activity were 117 nM and 36 nM, respectively.
Kimura
Yoshio
Y
Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan. kimura@ag.kagawa-u.ac
Kakemizu
Aoi
A
Matsubara
Yuuko
Y
Takegawa
Kaoru
K
D000595:Amino Acid Sequence; D020134:Catalytic Domain; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007700:Kinetics; D008969:Molecular Sequence Data; D016941:Myxococcus xanthus / Q000235:genetics*; D051579:Neurogranin / Q000737:chemistry; D009842:Oligopeptides / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
D004791:Enzyme Inhibitors; D009842:Oligopeptides; D010455:Peptides; D011994:Recombinant Proteins; D051579:Neurogranin; C037642:kemptide; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C