McGuinness T L, Lai Y, Greengard P
J Biol Chem. 1985 Feb 10;260(3):1696-704.
Ca2+/calmodulin-dependent protein kinase II, an abundant brain protein proposed to mediate a number of Ca2+-regulated processes in neuronal tissue, is composed of autophosphorylatable subunits of Mr 50,000 and 60,000/58,000. A recent study (McGuinness, T. L., Lai, Y., Greengard, P., Woodgett, J.R., and Cohen, P. (1983) FEBS Lett. 163, 329-334) suggested that this kinase exists as isozymes which vary in the relative ratio of these subunits in different tissues or species. Other studies (Walaas, S. I., Nairn, A. C., and Greengard, P. (1983) J. Neurosci. 3, 291-301, 302-311) provided evidence which suggested that the ratio of these phosphopeptides might vary in different brain regions. In the present investigation, we have tested this possibility by comparing Ca2+/calmodulin-dependent protein kinase II purified from rat forebrain and cerebellum. The two kinases had similar purification characteristics, subunit compositions, physical properties, and substrate specificities. Gel filtration and sucrose density gradient centrifugation provided an estimated molecular weight of 550,000 for the forebrain kinase and 615,000 for the cerebellar kinase. The kinases from the two regions clearly differed in the relative proportions of the Mr 50,000 and 60,000/58,000 subunits. Three independent methods indicated that the forebrain kinase contained the Mr 50,000/(60,000/58,000) subunits in approximately a 3:1 ratio, while the cerebellar kinase contained the Mr 50,000/(60,000/58,000) subunits in approximately a 1:4 ratio. The forebrain kinase subunits were shown to be identical to the corresponding subunits of the cerebellar kinase by several criteria. The data are consistent with the existence in various brain regions of isozymic forms of Ca2+/calmodulin-dependent protein kinase II which differ in their relative subunit ratios.
钙/钙调蛋白依赖性蛋白激酶II是一种在脑内含量丰富的蛋白质，被认为介导神经元组织中许多受钙调节的过程，它由分子量为50,000和60,000/58,000的可自身磷酸化的亚基组成。最近的一项研究（麦吉尼斯，T.L.，赖，Y.，格林加德，P.，伍德盖特，J.R.，和科恩，P.（1983年）《欧洲生物化学学会联合会快报》163，329 - 334）表明，这种激酶以同工酶的形式存在，在不同组织或物种中这些亚基的相对比例有所不同。其他研究（瓦拉斯，S.I.，奈恩，A.C.，和格林加德，P.（1983年）《神经科学杂志》3，291 - 301，302 - 311）提供的证据表明，这些磷酸肽的比例在不同脑区可能有所不同。在本研究中，我们通过比较从大鼠前脑和小脑中纯化的钙/钙调蛋白依赖性蛋白激酶II来检验这种可能性。这两种激酶具有相似的纯化特性、亚基组成、物理性质和底物特异性。凝胶过滤和蔗糖密度梯度离心法测得前脑激酶的分子量约为550,000，小脑激酶的分子量约为615,000。来自这两个脑区的激酶在分子量为50,000和60,000/58,000的亚基的相对比例上明显不同。三种独立的方法表明，前脑激酶中分子量为50,000/(60,000/58,000)的亚基比例约为3:1，而小脑激酶中分子量为50,000/(60,000/58,000)的亚基比例约为1:4。通过几个标准表明，前脑激酶的亚基与小脑激酶的相应亚基相同。这些数据与在不同脑区存在钙/钙调蛋白依赖性蛋白激酶II的同工酶形式一致，这些同工酶形式的亚基相对比例不同。
