title: Insights into the architecture of the eIF2Bα/β/δ regulatory subcomplex.
abstract: Eukaryotic translation initiation factor 2B (eIF2B), the guanine nucleotide exchange factor for the G-protein eIF2, is one of the main targets for the regulation of protein synthesis. The eIF2B activity is inhibited in response to a wide range of stress factors and diseases, including viral infections, hypoxia, nutrient starvation, and heme deficiency, collectively known as the integrated stress response. eIF2B has five subunits (α-ε). The α, β, and δ subunits are homologous to each other and form the eIF2B regulatory subcomplex, which is believed to be a trimer consisting of monomeric α, β, and δ subunits. Here we use a combination of biophysical methods, site-directed mutagenesis, and bioinformatics to show that the human eIF2Bα subunit is in fact a homodimer, at odds with the current trimeric model for the eIF2Bα/β/δ regulatory complex. eIF2Bα dimerizes using the same interface that is found in the homodimeric archaeal eIF2Bα/β/δ homolog aIF2B and related metabolic enzymes. We also present evidence that the eIF2Bβ/δ binding interface is similar to that in the eIF2Bα2 homodimer. Mutations at the predicted eIF2Bβ/δ dimer interface cause genetic neurological disorders in humans. We propose that the eIF2B regulatory subcomplex is an α2β2δ2 hexamer, composed of one α2 homodimer and two βδ heterodimers. Our results offer novel insights into the architecture of eIF2B and its interactions with the G-protein eIF2.
authors.affiliation: Department of Physiology and Biophysics, Boston University School of Medicine , Boston, Massachusetts 02118, United States.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Bogorad
authors.forename: Bing
authors.initials: B
authors.lastname: Xia
authors.forename: Dana G
authors.initials: DG
authors.lastname: Sandor
authors.forename: Artem B
authors.initials: AB
authors.lastname: Mamonov
authors.forename: Tanya R
authors.initials: TR
authors.lastname: Cafarella
authors.forename: Stefan
authors.initials: S
authors.lastname: Jehle
authors.forename: Sandor
authors.initials: S
authors.lastname: Vajda
authors.forename: Dima
authors.initials: D
authors.lastname: Kozakov
authors.forename: Assen
authors.initials: A
authors.lastname: Marintchev
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry; D020717:Eukaryotic Initiation Factor-2B / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics
chemical_list: D019843:Archaeal Proteins; D020717:Eukaryotic Initiation Factor-2B; D021122:Protein Subunits