Kimball S R, Jefferson L S
Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey 17033, USA.
Biochem Biophys Res Commun. 1995 Jul 26;212(3):1074-81. doi: 10.1006/bbrc.1995.2079.
Previous studies have shown that eIF-2B purified from rabbit reticulocytes binds ATP and that the binding is prevented by NADP+. Because NADP+ inhibits the activity of eIF-2B in in vitro reactions we have examined whether or not the activity of eIF-2B is modulated by ATP. In these studies, eIF-2B, purified from rat liver, was incubated with ATP prior to assay. We found that the activity of eIF-2B was inhibited with an IC50 of approximately 0.8 mM. The inhibition was not due to phosphorylation of the factor. However, the inhibition of eIF-2B activity caused by ATP could be prevented by coincubation with either NADPH or fructose-1,6-bisphosphate. The activity of eIF-2B was also inhibited following addition of either ATP or AMPPNP to a post-mitochondrial supernatant prepared from rat liver. Therefore, it is possible that the activity of eIF-2B might be allosterically regulated in vivo not only by changes in the redox state of pyridine dinucleotides but also by changes in the relative amounts of NADPH and ATP.
先前的研究表明，从兔网织红细胞中纯化的真核起始因子2B（eIF-2B）能结合ATP，且这种结合会被NADP⁺抑制。由于NADP⁺在体外反应中会抑制eIF-2B的活性，我们研究了eIF-2B的活性是否受ATP调节。在这些研究中，从大鼠肝脏中纯化的eIF-2B在测定前先与ATP孵育。我们发现eIF-2B的活性受到抑制，半数抑制浓度（IC50）约为0.8 mM。这种抑制并非由于该因子的磷酸化。然而，与NADPH或果糖-1,6-二磷酸共同孵育可防止ATP对eIF-2B活性的抑制。向从大鼠肝脏制备的线粒体后上清液中添加ATP或AMPPNP后，eIF-2B的活性也受到抑制。因此，eIF-2B的活性在体内可能不仅受到吡啶二核苷酸氧化还原状态变化的变构调节，还受到NADPH和ATP相对含量变化的调节。
