title: Involvement of protein IF2 N domain in ribosomal subunit joining revealed from architecture and function of the full-length initiation factor.
abstract: Translation initiation factor 2 (IF2) promotes 30S initiation complex (IC) formation and 50S subunit joining, which produces the 70S IC. The architecture of full-length IF2, determined by small angle X-ray diffraction and cryo electron microscopy, reveals a more extended conformation of IF2 in solution and on the ribosome than in the crystal. The N-terminal domain is only partially visible in the 30S IC, but in the 70S IC, it stabilizes interactions between IF2 and the L7/L12 stalk of the 50S, and on its deletion, proper N-formyl-methionyl(fMet)-tRNA(fMet) positioning and efficient transpeptidation are affected. Accordingly, fast kinetics and single-molecule fluorescence data indicate that the N terminus promotes 70S IC formation by stabilizing the productive sampling of the 50S subunit during 30S IC joining. Together, our data highlight the dynamics of IF2-dependent ribosomal subunit joining and the role played by the N terminus of IF2 in this process.
authors.affiliation: Centre for Integrative Biology, Department of Integrated Structural Biology, Institute of Genetics and of Molecular and Cellular Biology, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche 7104, Institut National de la Santé de la Recherche Médicale U964, Université de Strasbourg, 67404 Illkirch, France.
authors.forename: Angelita
authors.initials: A
authors.lastname: Simonetti
authors.forename: Stefano
authors.initials: S
authors.lastname: Marzi
authors.forename: Isabelle M L
authors.initials: IM
authors.lastname: Billas
authors.forename: Albert
authors.initials: A
authors.lastname: Tsai
authors.forename: Attilio
authors.initials: A
authors.lastname: Fabbretti
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Myasnikov
authors.forename: Pierre
authors.initials: P
authors.lastname: Roblin
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Vaiana
authors.forename: Isabelle
authors.initials: I
authors.lastname: Hazemann
authors.forename: Daniel
authors.initials: D
authors.lastname: Eiler
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Steitz
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Puglisi
authors.forename: Claudio O
authors.initials: CO
authors.lastname: Gualerzi
authors.forename: Bruno P
authors.initials: BP
authors.lastname: Klaholz
mesh_terms: D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D050505:Mutant Proteins / Q000378:metabolism; D010442:Peptide Chain Initiation, Translational; D039881:Prokaryotic Initiation Factor-2 / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D054657:Ribosome Subunits / Q000378:metabolism*; D054681:Ribosome Subunits, Large, Bacterial; D054680:Ribosome Subunits, Small, Bacterial; D053838:Scattering, Small Angle; D013329:Structure-Activity Relationship; D016963:Thermus thermophilus / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D050505:Mutant Proteins; D039881:Prokaryotic Initiation Factor-2
keywords: integrated structural biology; protein synthesis
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