H-1 AND N-15 RESONANCE ASSIGNMENTS AND STRUCTURE OF THE N-TERMINAL DOMAIN OF ESCHERICHIA-COLI INITIATION-FACTOR-3

Initiation factor IF3 from Escherichia coli is composed of two domains connected by a hydrophilic peptide. In this study, the N-terminal domain (residues 7-83) has been overexpressed, N-15 labelled and purified. NMR assignments for this domain have been obtained by two-dimensional and three-dimensional heteronuclear and homonuclear spectroscopy. Using distance geometry and simulated annealing, a three-dimensional solution structure was calculated using 506 NOE and 56 dihedral angle restraints. The resulting structure is composed of a five-stranded antiparallel beta sheet surrounded by two alpha helices. Since the heteronuclear H-1-N-15 correlation spectrum of the N-terminal domain of IF3 is an almost exact subset of that of the native protein, the assignments obtained and the structure calculated should be directly transposable to the full-length protein.