Interaction of fMet-tRNA fMet with the C-terminal domain of translational initiation factor IF2 from Bacillus stearothermophilus

Abstract

Analytical ultracentrifugation studies indicated that the C-terminal domains of IF2 comprising amino acid residues 520–741 (IF2 C) and 632–741 (IF2 C-2) bind fMet-tRNA with similar affinities ( K d at 25°C equal to 0.27 and 0.23 μM, respectively). Complex formation between fMet-tRNA fMet and IF2 C or IF2 C-2 is accompanied by barely detectable spectral changes as demonstrated by a comparison of the Raman spectra of the complexes with the calculated sum of the spectra of the individual components. These results and the temperature dependence of the K d of the protein–RNA complexes indicate that complex formation is not accompanied by obvious conformational changes of the components, and possibly depends on a rather small binding site comprising only a few interacting residues of both components.