Inoue S, Mizutani A, Sugita R, Sugita K, Hidaka H
Department of Pharmacology, Nagoya University School of Medicine, Japan.
Biochem Biophys Res Commun. 1995 Oct 24;215(3):861-7. doi: 10.1006/bbrc.1995.2543.
A protein activator of Ca2+/calmodulin (CaM)-dependent protein kinase I was purified from rat brain. The activator was retained on a CaM-Sepharose column in the presence of Ca2+ and kinase assay of renatured gel revealed the 64 kDa molecule in the purified activator fraction to be autophosphorylated and to phosphorylate recombinant CaM kinase I in the presence of Ca2+/calmodulin. These results suggest that this activator of CaM kinase I is also a CaM-dependent protein kinase. Phosphorylation of CaM kinase I by the activator resulted in drastic potentiation of its CaM-dependent activity. Furthermore, kinetic analyses demonstrated that the activation decreases the Km values of CaM kinase I for both ATP and syntide-2 without a change in Vmax values. Considering the quite low enzymatic activity of recombinant CaM kinase I without activation, the 64 kDa species might be essential for CaM kinase I function in vivo.
从大鼠脑中纯化出一种钙/钙调蛋白（CaM）依赖性蛋白激酶I的蛋白激活剂。在Ca2+存在的情况下，该激活剂保留在CaM-琼脂糖柱上，复性凝胶的激酶分析显示，纯化的激活剂组分中的64 kDa分子在Ca2+/钙调蛋白存在下会发生自磷酸化，并能磷酸化重组CaM激酶I。这些结果表明，这种CaM激酶I的激活剂也是一种CaM依赖性蛋白激酶。激活剂对CaM激酶I的磷酸化导致其CaM依赖性活性急剧增强。此外，动力学分析表明，这种激活作用降低了CaM激酶I对ATP和合成肽-2的Km值，而Vmax值不变。鉴于未激活的重组CaM激酶I酶活性相当低，64 kDa的蛋白可能对CaM激酶I在体内的功能至关重要。
