Welsh G I, Price N T, Bladergroen B A, Bloomberg G, Proud C G
Department of Biochemistry, School of Medical Sciences, University of Bristol, United Kingdom.
Biochem Biophys Res Commun. 1994 Jun 30;201(3):1279-88. doi: 10.1006/bbrc.1994.1843.
Initiation factor eIF-2 (a trimer of subunits alpha, beta and gamma) attaches the initiator Met-tRNA to the ribosome during the initiation of translation in eukaryotic cells. Both the alpha and beta subunits can be phosphorylated although the sites in the beta-subunit have not previously been fully identified. Here we identify the sites at which eIF-2 beta is phosphorylated in vitro by three well-characterised protein kinases, casein kinase-2 (which phosphorylates serine residues-2 and -67), protein kinase C (serine-13) and cAMP-dependent protein kinase (serine-218). This constitutes an essential prerequisite for studying the phosphorylation of eIF-2 beta in vivo. Indeed, we present evidence that at least one of these sites (serine-67) is phosphorylated in reticulocytes. The major kinase activity against eIF-2 beta in reticulocyte lysates appears in CK-2 and protein phosphatase-2A is the principal enzyme responsible for dephosphorylation of eIF-2 beta phosphorylated by this kinase.
起始因子eIF-2（由α、β和γ亚基组成的三聚体）在真核细胞翻译起始过程中，将起始甲硫氨酰 - tRNA附着到核糖体上。α和β亚基都可以被磷酸化，尽管β亚基上的位点此前尚未完全确定。在这里，我们确定了eIF-2β在体外被三种特征明确的蛋白激酶磷酸化的位点，即酪蛋白激酶2（磷酸化丝氨酸残基 - 2和 - 67）、蛋白激酶C（丝氨酸 - 13）和cAMP依赖性蛋白激酶（丝氨酸 - 218）。这是研究体内eIF-2β磷酸化的一个必要前提。事实上，我们提供的证据表明，这些位点中至少有一个（丝氨酸 - 67）在网织红细胞中被磷酸化。网织红细胞裂解物中针对eIF-2β的主要激酶活性来自CK-2，而蛋白磷酸酶2A是负责使被该激酶磷酸化的eIF-2β去磷酸化的主要酶。
