Conformational Ensembles of the Disordered 4E-BP2:eIF4E Complex Restrained by smFRET Experiments

Area of Science:

• Molecular Biology
• Structural Biology
• Biophysics

Background:

• Eukaryotic translation initiation is a key regulatory point in gene expression.
• Eukaryotic initiation factor 4E (eIF4E) binding to 4E-binding proteins (4E-BPs) regulates this process.
• 4E-BPs are intrinsically disordered proteins, posing challenges for structural determination.

Purpose of the Study:

• To generate and analyze atomistic conformational ensembles of 4E-BP2 and its complex with eIF4E.
• To compare the structural dynamics of free 4E-BP2 and its bound state.
• To elucidate the structural basis of translation regulation by the 4E-BP2:eIF4E complex.

Main Methods:

• IDPConformerGenerator and X-EISDv2 workflow for generating conformational ensembles.
• Integration of single-molecule fluorescence and NMR data.
• Validation using solution spectroscopy and comparison with crystal structure data.

Main Results:

• Generated full-length atomistic conformational ensembles for apo 4E-BP2 and the 4E-BP2:eIF4E complex.
• Observed delocalization of contacts and identified two new contact regions between disordered termini.
• Validated ensemble models with experimental data, supporting a dynamic binding interface.

Conclusions:

• The dynamic nature of the 4E-BP2:eIF4E complex is crucial for translation regulation.
• Newly identified contact regions suggest allosteric roles in modulating binding affinity.
• The findings support a model where the complex's dynamics facilitate regulatory site accessibility.