title: Structural transitions of translation initiation factor IF2 upon GDPNP and GDP binding in solution.
abstract: Three protein factors ensure rapid and accurate initiation of translation in bacteria. Translation initiation factor IF2 is a ribosome-dependent GTPase, which is important for correct positioning of initiator tRNA on the 30S subunit as well as ribosomal subunit joining. The solution structure of the free C-terminal part of IF2 (IF2C, comprising domains IV to VI-2) was previously determined by small-angle X-ray scattering (SAXS) [Rasmussen, L. C., et al. (2008) Biochemistry 47, 5590-5598]. In this study, adding GDP or nonhydrolyzable GTP analogue GDPNP to the protein in solution caused structural changes in the protein, in agreement with recent data determined via isothermal titration calorimetry [Hauryliuk, V., et al. (2009) J. Mol. Biol. 394, 621-626]. The p(r) function indicated an elongated conformation supported by radii of gyration of 40.1 and 44.9 Å and maximum dimensions of ~125 and ~150 Å for IF2C with GDPNP and GDP, respectively. The SAXS data were used to model the structure of IF2C bound to either GDPNP or GDP. The structural transitions of IF2C upon GDPNP binding and following nucleotide hydrolysis support the concept of cofactor-dependent conformational switching rather than the classical model for GTPase activity.
authors: Department of Molecular Biology, Aarhus University, Gustav Wieds Vej 10, DK-8000 Aarhus C, Denmark.
authors: Louise Carøe
authors: LC
authors: Vohlander Rasmussen
authors: Cristiano Luis Pinto
authors: CL
authors: Oliveira
authors: Jan Skov
authors: JS
authors: Pedersen
authors: Hans Uffe
authors: HU
authors: Sperling-Petersen
authors: Kim Kusk
authors: KK
authors: Mortensen
mesh_terms: D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D039881:Prokaryotic Initiation Factor-2 / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle; D012996:Solutions; D014961:X-Ray Diffraction
chemical_list: D029968:Escherichia coli Proteins; C503923:GDPNP compound; D008024:Ligands; D039881:Prokaryotic Initiation Factor-2; D012996:Solutions; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate