|Ribosome-associated cyclic nucleotide-independent protein kinase of Artemia salina cryptobiotic gastrulae|Thoen, C.; Slegers, H. (1985). Ribosome-associated cyclic nucleotide-independent protein kinase of Artemia salina cryptobiotic gastrulae. Biochim. Biophys. Acta 825(3): 268-279. dx.doi.org/10.1016/0167-4781(85)90014-4
In: Biochimica et Biophysica Acta. Elsevier: Amsterdam. ISSN 0006-3002, more
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An extra-ribosomal cAMP-independent protein kinase from cryptobiotic embryos of Artemia salina has been purified to near homogeneity by gel filtration on Bio-Gel A-0.5 m, ion-exchange chromatography on DEAE-cellulose and phosphocellulose P11 and affinity chromatography on casein-Sepharose 4B and ATP-agarose. The enzymatic activity has a broad optimum at pH 7–8. Maximal activity is obtained in the presence of 5–6 mM MgCl2. The activity is inhibited by Mn2+, Ca2+ and K+. The enzyme has an Mr of 127 000, utilizes both ATP and GTP as phosphoryl donors and is completely inhibited by heparin and poly(l-glutamic acid). According to its properties, the enzyme can be classified as a casein kinase type II. Although the enzyme is associated with ribosomes, ribosomal proteins are not among the main substrates. The kinase is able to phosphorylate both the α and the β subunits of initiation factor eIF2 using ATP or GTP as phosphoryl donors. The function of phosphorylation in the initiation of protein synthesis is discussed.