title: Identification of interprotein interactions between the subunits of eukaryotic initiation factors eIF2 and eIF2B.
abstract: Modulation of protein/protein interaction is an important mechanism involved in regulation of translation initiation. Specifically, regulation of the interaction of eIF2 with the guanine nucleotide exchange factor, eIF2B, is a key mechanism for controlling translation under a variety of conditions. Phosphorylation of the alpha-subunit of eIF2 converts the protein into a competitive inhibitor of eIF2B by causing an increase in the binding affinity of eIF2B for eIF2. Consequently, it has been assumed that the alpha-subunit of eIF2 is directly involved in binding to eIF2B. In the present study, eIF2 was found to bind only to the delta- and epsilon-subunits of eIF2B, and eIF2B was shown to bind only to the beta-subunit of eIF2 by far-Western blot analysis. The binding site on eIF2beta for either the eIF2B holoprotein, or the isolated delta- or epsilon-subunits of eIF2B was shown to be located within approximately 70 amino acids of the C terminus of the protein. Phosphorylation of the alpha-subunit of eIF2 did not promote binding of eIF2B to the isolated subunit. However, it did cause an increase in the affinity of eIF2B for eIF2. Finally, phosphorylation by protein kinase A of the beta-subunit of eIF2 in the C-terminal portion of the protein increased the guanine nucleotide exchange activity of eIF2B, whereas phosphorylation by casein kinase II or protein kinase C was without effect.
authors.affiliation: Department of Cellular and Molecular Physiology, The Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033, USA. scot.kimball@hmc.psu.edu
authors.forename: S R
authors.initials: SR
authors.lastname: Kimball
authors.forename: N K
authors.initials: NK
authors.lastname: Heinzinger
authors.forename: R L
authors.initials: RL
authors.lastname: Horetsky
authors.forename: L S
authors.initials: LS
authors.lastname: Jefferson
mesh_terms: D000818:Animals; D001665:Binding Sites; D047390:Casein Kinase II; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry*; D020717:Eukaryotic Initiation Factor-2B; D020662:Guanine Nucleotide Exchange Factors; D016296:Mutagenesis; D010442:Peptide Chain Initiation, Translational; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000737:chemistry*; D051381:Rats
chemical_list: D015852:Eukaryotic Initiation Factor-2; D020717:Eukaryotic Initiation Factor-2B; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C