Mechanism of Phosphorylation-Induced Folding of 4E-BP2 Revealed by Molecular Dynamics Simulations

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biophysics

Background:

• Intrinsically disordered proteins (IDPs) undergo functional conformational changes.
• Site-specific phosphorylation of eukaryotic translation initiation factor 4E-binding protein isoform 2 (4E-BP2) can alter its function by inducing folding.
• The precise mechanism of phosphorylation-induced folding in 4E-BP2 remains unclear.

Purpose of the Study:

• To investigate the mechanism by which phosphorylation at threonine 37 (T37) and threonine 46 (T46) induces folding in 4E-BP2.
• To elucidate the role of phosphorylated T37 and T46 in stabilizing the folded structure and influencing the unfolded ensemble.
• To provide molecular insights into the effects of site-specific phosphorylation on protein structure and dynamics.

Main Methods:

• All-atom molecular dynamics (MD) simulations were employed.
• Simulations were performed on both folded and unfolded states of 4E-BP2.
• Different phosphorylation states of T37 and T46 were analyzed.

Main Results:

• Phosphorylation of both T37 and T46 significantly stabilizes the folded structure of 4E-BP2, particularly β-turns and the binding motif.
• Phosphorylated residues act as nucleation sites, guiding protein folding through intermediate states via hydrogen bonding.
• The phosphorylation-induced conformational changes affect the distribution of the unfolded ensemble, with T46 phosphorylation potentially initiating folding earlier than T37.

Conclusions:

• Site-specific phosphorylation is a critical determinant of 4E-BP2 structure and dynamics.
• Phosphorylated residues play a direct role in nucleating and stabilizing protein folding.
• These findings offer novel insights into the regulatory mechanisms of IDPs through post-translational modifications.