title: Structure of the ternary initiation complex aIF2-GDPNP-methionylated initiator tRNA.
abstract: Eukaryotic and archaeal translation initiation factor 2 (e/aIF2) is a heterotrimeric GTPase that has a crucial role in the selection of the correct start codon on messenger RNA. We report the 5-Å resolution crystal structure of the ternary complex formed by archaeal aIF2 from Sulfolobus solfataricus, the GTP analog GDPNP and methionylated initiator tRNA. The 3D model is further supported by solution studies using small-angle X-ray scattering. The tRNA is bound by the α and γ subunits of aIF2. Contacts involve the elbow of the tRNA and the minor groove of the acceptor stem, but not the T-stem minor groove. We conclude that despite considerable structural homology between the core γ subunit of aIF2 and the elongation factor EF1A, these two G proteins of the translation apparatus use very different tRNA-binding strategies.
authors.affiliation: Laboratoire de Biochimie, Unité mixte de Recherche 7654, Ecole Polytechnique, Centre National de la Recherche Scientifique, Palaiseau, France. emma@botrytis.polytechnique.fr
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Schmitt
authors.forename: Michel
authors.initials: M
authors.lastname: Panvert
authors.forename: Christine
authors.initials: C
authors.lastname: Lazennec-Schurdevin
authors.forename: Pierre-Damien
authors.initials: PD
authors.lastname: Coureux
authors.forename: Javier
authors.initials: J
authors.lastname: Perez
authors.forename: Andrew
authors.initials: A
authors.lastname: Thompson
authors.forename: Yves
authors.initials: Y
authors.lastname: Mechulam
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010448:Peptide Initiation Factors / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D019642:RNA, Archaeal / Q000737:chemistry* / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000737:chemistry* / Q000378:metabolism; D048229:Sulfolobus solfataricus / Q000737:chemistry* / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; C503923:GDPNP compound; D010448:Peptide Initiation Factors; D021122:Protein Subunits; D019642:RNA, Archaeal; D012358:RNA, Transfer, Met; C116557:initiation factor 2, archaeal; D006160:Guanosine Triphosphate