Full activation of brain calmodulin-dependent protein kinase IV requires phosphorylation of the amino-terminal serine-rich region by calmodulin-dependent protein kinase IV kinase.
Rat brain calmodulin-dependent protein kinase IV (CaM-kinase IV) was activated approximately 20 to 30-fold by incubation with CaM-kinase IV kinase purified from rat brain under the Ca2+/calmodulin-dependent phosphorylation conditions. When CaM-kinase IV was incubated without CaM-kinase IV kinase, no significant activation was observed, indicating that the marked activation of CaM-kinase IV occurred as a result of the action of CaM-kinase IV kinase. More than 3 mol of phosphate were incorporated into 1 mol of the enzyme after incubation with CaM-kinase IV kinase at 30 degrees C for 20 min, but the activation occurred upon the initial incorporation of 1 mol of phosphate. The rate of the initial phosphorylation increased when the amount of CaM-kinase IV kinase added into the reaction mixture increased, but the rate of phosphorylation following the initial phosphorylation did not increase, suggesting that the initial phosphorylation was catalyzed by CaM-kinase IV kinase, and that subsequent phosphorylation was catalyzed by CaM-kinase IV itself activated by CaM-kinase IV kinase. The initial phosphorylation occurred in the amino-terminal serine-rich region of CaM-kinase IV. Kinetic analysis revealed that the increase in the activity upon phosphorylation was due mainly to an increase in the Vmax values.
Okuno
S
S
Department of Biochemistry, Asahikawa Medical College, Hokkaido.
Kitani
T
T
Fujisawa
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D051381:Rats
D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517686:Camk4 protein, rat