Allosteric Regulation of Eukaryotic Initiation Factor eIF-2B by Adenine Nucleotides

• Published in: Biochemical and biophysical research communications Vol. 212; no. 3; pp. 1074 - 1081
• Main Authors: Kimball, S.R., Jefferson, L.S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 26.07.1995
• Subjects: Adenine Nucleotides - pharmacology; Adenosine Triphosphate - pharmacology; Adenylyl Imidodiphosphate - pharmacology; Allosteric Regulation; Animals; Casein Kinase II; Fructosediphosphates - pharmacology; Guanine Nucleotide Exchange Factors; In Vitro Techniques; Liver - metabolism; NADP - pharmacology; Oxidation-Reduction; Phosphorylation; Protein-Serine-Threonine Kinases - pharmacology; Proteins - antagonists & inhibitors; Proteins - metabolism; Rats
• ISSN: 0006-291X; 1090-2104
• 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 postmitochondrial 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.