title: Crystal structure of eukaryotic translation initiation factor 2B.
abstract: Eukaryotic cells restrict protein synthesis under various stress conditions, by inhibiting the eukaryotic translation initiation factor 2B (eIF2B). eIF2B is the guanine nucleotide exchange factor for eIF2, a heterotrimeric G protein consisting of α-, β- and γ-subunits. eIF2B exchanges GDP for GTP on the γ-subunit of eIF2 (eIF2γ), and is inhibited by stress-induced phosphorylation of eIF2α. eIF2B is a heterodecameric complex of two copies each of the α-, β-, γ-, δ- and ε-subunits; its α-, β- and δ-subunits constitute the regulatory subcomplex, while the γ- and ε-subunits form the catalytic subcomplex. The three-dimensional structure of the entire eIF2B complex has not been determined. Here we present the crystal structure of Schizosaccharomyces pombe eIF2B with an unprecedented subunit arrangement, in which the α2β2δ2 hexameric regulatory subcomplex binds two γε dimeric catalytic subcomplexes on its opposite sides. A structure-based in vitro analysis by a surface-scanning site-directed photo-cross-linking method identified the eIF2α-binding and eIF2γ-binding interfaces, located far apart on the regulatory and catalytic subcomplexes, respectively. The eIF2γ-binding interface is located close to the conserved 'NF motif', which is important for nucleotide exchange. A structural model was constructed for the complex of eIF2B with phosphorylated eIF2α, which binds to eIF2B more strongly than the unphosphorylated form. These results indicate that the eIF2α phosphorylation generates the 'nonproductive' eIF2-eIF2B complex, which prevents nucleotide exchange on eIF2γ, and thus provide a structural framework for the eIF2B-mediated mechanism of stress-induced translational control.
authors.affiliation: Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.|RIKEN Systems and Structural Biology Center, Tsurumi-ku, Yokohama 230-0045, Japan.|RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kashiwagi
authors.affiliation: RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Madoka
authors.initials: M
authors.lastname: Nishimoto
authors.affiliation: Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.|RIKEN Systems and Structural Biology Center, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Takuya B
authors.initials: TB
authors.lastname: Hiyama
authors.affiliation: RIKEN Systems and Structural Biology Center, Tsurumi-ku, Yokohama 230-0045, Japan.|RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Higo
authors.affiliation: RIKEN Systems and Structural Biology Center, Tsurumi-ku, Yokohama 230-0045, Japan.|RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Umehara
authors.affiliation: RIKEN Systems and Structural Biology Center, Tsurumi-ku, Yokohama 230-0045, Japan.|RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Sakamoto
authors.affiliation: Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.|RIKEN Systems and Structural Biology Center, Tsurumi-ku, Yokohama 230-0045, Japan.|RIKEN Center for Life Science Technologies, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Takuhiro
authors.initials: T
authors.lastname: Ito
authors.affiliation: Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.|RIKEN Systems and Structural Biology Center, Tsurumi-ku, Yokohama 230-0045, Japan.|RIKEN Structural Biology Laboratory, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D055162:Biocatalysis; D003432:Cross-Linking Reagents / Q000737:chemistry; D018360:Crystallography, X-Ray; D020717:Eukaryotic Initiation Factor-2B / Q000737:chemistry* / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008958:Models, Molecular; D010766:Phosphorylation; D011485:Protein Binding; D014176:Protein Biosynthesis; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012568:Schizosaccharomyces / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D020717:Eukaryotic Initiation Factor-2B; D021122:Protein Subunits; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate