The cap-binding protein eIF4E promotes folding of a functional domain of yeast translation initiation factor eIF4G1

The association of eucaryotic translation initiation factor eLF4G with the cap-binding protein eIF4E establishes a critical link between the mRNA and the ribosome during translation initiation. This association requires a con served seven amino acid peptide within eIF4G that binds to eIF4E, Here we r eport that a 98-amino acid fragment of S. cerevisiae eIF4G1 that contains t his eIF4E binding peptide undergoes an unfolded to folded transition upon b inding to eIF4E. The folding of the eIF4G1 domain was evidenced by the eIF4 E-dependent changes in its protease sensitivity and H-1-N-15 HSQC NMR spect rum. Analysis of a series of charge-to-alanine mutations throughout the ess ential 55.4-kDa core of yeast eIF4G1 also revealed substitutions within thi s 98-amino acid region that led to reduced eIF4E binding in vivo and in vit ro. These data suggest that the association of yeast eIF4E with eIF4G1 lead s to the formation of a structured domain within eIF4G1 that could serve as a specific site for interactions with other components of the translationa l apparatus. They also suggest that the stability of the native eIF4E-eIF4G complex is determined by amino acid residues outside of the conserved seve n-residue consensus sequence.