期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：2
页码：789-793
DOI：10.1073/pnas.75.2.789
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Initiation factor 2 (eIF-2) is phosphorylated in vitro by two different cyclic nucleotide-independent protein kinases. As previously shown, a protein kinase activity that comigrates with the major casein kinase activity from rabbit reticulocytes phosphorylates eIF-2beta. In addition, a second protein kinase that specifically phosphorylates eIF-2alpha has been identified. Both protein kinase activities demonstrate cyclic nucleotide-independent activity and are not inhibited by the inhibitor protein diagnostic for cyclic AMP-regulated protein kinase activities. Phosphorylation of eIF-2alpha is almost completely inhibited by 20--35 muM hemin, whereas phosphorylation of eIF-2beta is only partially inhibited. Hemin acts by decreasing the rate of incorporation of phosphate into eIF-2alpha. The protein kinase activity that modifies eIF-2alpha has been shown to have inhibitory activity in the cell-free protein-synthesizing system, whereas the protein kinase for eIF-2beta has no effect. The identity of the former enzyme with the hemin-controlled repressor and role of hemin in the control of initiation are discussed.
