A conserved motif within the flexible C-terminus of the translational regulator 4E-BP is required for tight binding to the mRNA cap-binding protein eIF4E.

Although the central α-helical Y(X)4LΦ motif (X, variable amino acid; Φ, hydrophobic amino acid) of the translational regulator 4E-BP [eIF (eukaryotic initiation factor) 4E-binding protein] is the core binding region for the mRNA cap-binding protein eIF4E, the functions of its N- and C-terminal flexible regions for interaction with eIF4E remain to be elucidated. To identify the role for the C-terminal region in such an interaction, the binding features of full-length and sequential C-terminal deletion mutants of 4E-BPn (n=1-3) subtypes were investigated by SPR (surface plasmon resonance) analysis and ITC (isothermal titration calorimetry). Consequently, the conserved PGVTS/T motif within the C-terminal region was shown to act as the second binding region and to play an important role in the tight binding to eIF4E.