Allosteric regulation of eukaryotic initiation factor eIF-2B by adenine nucleotides.
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.
Kimball
S R
SR
Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey 17033, USA.
Jefferson
L S
LS
D000227:Adenine Nucleotides / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000494:Allosteric Regulation; D000818:Animals; D047390:Casein Kinase II; D005635:Fructosediphosphates / Q000494:pharmacology; D020662:Guanine Nucleotide Exchange Factors; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism; D009249:NADP / Q000494:pharmacology; D010084:Oxidation-Reduction; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000494:pharmacology; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats
D000227:Adenine Nucleotides; D005635:Fructosediphosphates; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D000266:Adenylyl Imidodiphosphate; D009249:NADP; D000255:Adenosine Triphosphate; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; C029063:fructose-1,6-diphosphate