4E binding proteins inhibit the translation factor eIF4E without folded structure

Area of Science:

• Molecular Biology
• Protein Structure and Function
• Gene Regulation

Background:

• 4E binding proteins (4E-BPs) are key regulators of protein translation.
• They inhibit translation by interacting with the eukaryotic initiation factor 4E (eIF4E).
• The structural basis for this interaction and inhibition is not fully understood.

Purpose of the Study:

• To investigate the structural determinants of 4E-BP1 and 4E-BP2 function.
• To identify the specific regions of 4E-BPs responsible for eIF4E binding and translation inhibition.

Main Methods:

• Production of 4E-BPs in Escherichia coli.
• Nuclear Magnetic Resonance (NMR) and Circular Dichroism (CD) spectroscopy to assess protein structure.
• In vitro translation assays using reticulocyte lysate.
• Analysis of eIF4E binding to 4E-BPs and synthetic peptides.

Main Results:

• Recombinant 4E-BPs exhibited minimal folded structure by NMR and CD.
• Despite lacking defined structure, 4E-BPs effectively inhibited translation in vitro.
• A synthetic peptide corresponding to residues 49-68 of 4E-BP1 was sufficient for eIF4E binding and translation inhibition.
• NMR data indicated specific, limited interactions between 4E-BPs and eIF4E.

Conclusions:

• A short, central region of 4E-BPs (residues 49-68) is critical for eIF4E binding and translation inhibition.
• The majority of the 4E-BP protein structure is unfolded and flexible.
• This flexible structure facilitates the interaction with eIF4E to regulate translation.