How Peptides Bind to PSD-95/Discs-Large/ZO-1 Domains.

Area of Science:

• Biochemistry
• Structural Biology
• Computational Biology

Background:

• PDZ domains are crucial adaptor proteins mediating protein-protein interactions.
• They bind to the C-terminal tails of partner proteins, playing roles in various cellular processes.
• Understanding PDZ domain binding is key to deciphering signaling pathways.

Purpose of the Study:

• To characterize the binding modes of phosphorylated and unphosphorylated peptides to PDZ domains.
• To compare binding affinities and characteristics between different PDZ domains (hPTP1E PDZ2 and MAGI1 PDZ1).
• To assess the accuracy of molecular dynamics simulations in predicting peptide-PDZ interactions, including phosphorylation effects.

Main Methods:

• Extensive molecular dynamics (MD) simulations.
• Alchemical free energy calculations.
• Peptide-protein docking simulations (PaCS-MD).
• Analysis of binding characteristics, hydrogen bonding, and coordination.

Main Results:

• Simulations accurately reproduced known binding features like carboxyl tail coordination and beta-sheet hydrogen bonding.
• hPTP1E PDZ2 exhibited tighter coordination compared to MAGI1 PDZ1.
• Arginine mutations highlighted the importance of specific residues for peptide binding.
• Free energy calculations successfully predicted binding differences between unphosphorylated peptides and absolute binding free energy for one peptide.

Conclusions:

• Molecular dynamics simulations are valuable tools for studying PDZ domain interactions.
• Simulations can capture key binding determinants but may have limitations with phosphorylation.
• Further refinement of force fields is needed for accurate prediction of phosphorylated peptide binding.