title: Heteronuclear NMR studies of E. coli translation initiation factor IF3. Evidence that the inter-domain region is disordered in solution.
abstract: Initiation factor IF3 from Escherichia coli plays a critical role in the selection of the correct initiation codon. This protein is composed of two domains, connected by a lysin-rich hydrophilic linker. The conformation of native IF3 was investigated by heteronuclear NMR spectroscopy. The two domains are independent and show little or no interaction. Heteronuclear relaxation studies of a sample selectively labelled on lysine residues demonstrates that the inter-domain linker is highly flexible, exhibiting increased 15N T2 values and negative 1H[15N] nuclear Overhause effects over a length of at least eight residues. Analysis of the rotational correlation times further shows that the motions of the two domains are most likely uncorrelated. The inter-domain linker thus displays almost totally unrestricted motions. Accordingly, the amide protons in the central region are shown to be in fast exchange with water. Such a high degree of flexibility of the inter-domain linker might be required for IF3 domains to interact with distant regions of the ribosome.
authors.affiliation: Laboratoire de Synthèse Organique, URA 1308 du CNRS Ecole Polytechnique, Palaiseau, France.
authors.forename: M
authors.initials: M
authors.lastname: Moreau
authors.forename: E
authors.initials: E
authors.lastname: de Cock
authors.forename: P L
authors.initials: PL
authors.lastname: Fortier
authors.forename: C
authors.initials: C
authors.lastname: Garcia
authors.forename: C
authors.initials: C
authors.lastname: Albaret
authors.forename: S
authors.initials: S
authors.lastname: Blanquet
authors.forename: J Y
authors.initials: JY
authors.lastname: Lallemand
authors.forename: F
authors.initials: F
authors.lastname: Dardel
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D003198:Computer Simulation; D004926:Escherichia coli / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008961:Models, Structural; D009587:Nitrogen Isotopes; D010448:Peptide Initiation Factors / Q000737:chemistry* / Q000378:metabolism; D039665:Prokaryotic Initiation Factor-3; D011487:Protein Conformation; D012270:Ribosomes / Q000378:metabolism; D012996:Solutions
chemical_list: D001426:Bacterial Proteins; D009587:Nitrogen Isotopes; D010448:Peptide Initiation Factors; D039665:Prokaryotic Initiation Factor-3; D012996:Solutions