Sulakhe P V, Petrali E H, Davis E R, Thiessen B J
Biochemistry. 1980 Nov 11;19(23):5363-71. doi: 10.1021/bi00564a034.
Polypeptide composition and endogenous phosphorylation were investigated in the subfractions of rat brain myelin isolated by either discontinuous or continuous sucrose density gradient centrifugation of myelin. Similarly, a myelin-like membrane fraction (SN4) was also studied. Observations were made that strongly indicated the presence of a calcium-stimulated protein kinase in a highly purified myelin preparation and which exclusively phosphorylated myelin basic proteins of the membrane preparation. Adenosine cyclic 3',5'-phosphate (cAMP) stimulated kinase on the other hand was found to be considerably enriched in the myelin-like membrane fraction. Although this latter enzyme is also capable of phosphorylating the basic proteins, its effect was at least 5 times weaker compared to the calcium-stimulated myelin protein kinase. Within the gradient subfractions there appeared a close relation between the amount of basic proteins and their calcium-stimulated phosphorylation; a similar relationship, however, was not obtained in the case of cAMP-dependent phosphorylation of myelin basic proteins. The former (i.e., Ca2+-stimulated phosphorylation) was found to require a protein factor that functionally resembled calmodulin. The results thus raises an interesting possibility of the presence of calmodulin-like proteins and a calcium-stimulated protein kinase in adult myelin membrane from mammalian brain, both of which have been hitherto unrecognized constituents of myelin membranes.
通过对髓磷脂进行不连续或连续蔗糖密度梯度离心分离出大鼠脑髓磷脂亚组分，对其多肽组成和内源性磷酸化进行了研究。同样，也研究了一种类髓磷脂膜组分（SN4）。观察结果强烈表明，在高度纯化的髓磷脂制剂中存在一种钙刺激蛋白激酶，它专门使膜制剂中的髓磷脂碱性蛋白磷酸化。另一方面，发现腺苷环3',5'-磷酸（cAMP）刺激的激酶在类髓磷脂膜组分中大量富集。虽然这种后一种酶也能够使碱性蛋白磷酸化，但其作用与钙刺激的髓磷脂蛋白激酶相比至少弱5倍。在梯度亚组分中，碱性蛋白的量与其钙刺激的磷酸化之间似乎存在密切关系；然而，在髓磷脂碱性蛋白的cAMP依赖性磷酸化情况下，并未获得类似的关系。发现前者（即Ca2+刺激的磷酸化）需要一种在功能上类似于钙调蛋白的蛋白质因子。因此，这些结果提出了一种有趣的可能性，即在哺乳动物脑的成年髓磷脂膜中存在类钙调蛋白和钙刺激蛋白激酶，这两种物质迄今为止一直是髓磷脂膜中未被认识的成分。
