title: Roles of yeast eIF2α and eIF2β subunits in the binding of the initiator methionyl-tRNA.
abstract: Heterotrimeric eukaryotic/archaeal translation initiation factor 2 (e/aIF2) binds initiator methionyl-tRNA and plays a key role in the selection of the start codon on messenger RNA. tRNA binding was extensively studied in the archaeal system. The γ subunit is able to bind tRNA, but the α subunit is required to reach high affinity whereas the β subunit has only a minor role. In Saccharomyces cerevisiae however, the available data suggest an opposite scenario with β having the most important contribution to tRNA-binding affinity. In order to overcome difficulties with purification of the yeast eIF2γ subunit, we designed chimeric eIF2 by assembling yeast α and β subunits to archaeal γ subunit. We show that the β subunit of yeast has indeed an important role, with the eukaryote-specific N- and C-terminal domains being necessary to obtain full tRNA-binding affinity. The α subunit apparently has a modest contribution. However, the positive effect of α on tRNA binding can be progressively increased upon shortening the acidic C-terminal extension. These results, together with small angle X-ray scattering experiments, support the idea that in yeast eIF2, the tRNA molecule is bound by the α subunit in a manner similar to that observed in the archaeal aIF2-GDPNP-tRNA complex.
authors.affiliation: Laboratoire de Biochimie, Unité mixte de Recherche 7654, Ecole Polytechnique, Centre National de la Recherche Scientifique, F-91128 Palaiseau Cedex, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Naveau
authors.forename: Christine
authors.initials: C
authors.lastname: Lazennec-Schurdevin
authors.forename: Michel
authors.initials: M
authors.lastname: Panvert
authors.forename: Etienne
authors.initials: E
authors.lastname: Dubiez
authors.forename: Yves
authors.initials: Y
authors.lastname: Mechulam
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Schmitt
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics; D001483:Base Sequence; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012358:RNA, Transfer, Met / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D053838:Scattering, Small Angle; D017386:Sequence Homology, Amino Acid; D014961:X-Ray Diffraction
chemical_list: D019843:Archaeal Proteins; D015852:Eukaryotic Initiation Factor-2; D021122:Protein Subunits; D012358:RNA, Transfer, Met; D029701:Saccharomyces cerevisiae Proteins