Structural insights into phenylethanolamines high-affinity binding site in NR2B from binding and molecular modeling...

Area of Science:

• Neuroscience
• Biochemistry
• Structural Biology

Background:

• Phenylethanolamines, including ifenprodil, modulate N-methyl-D-aspartate (NMDA) receptor activity by binding to the NR2B subunit.
• Investigating the ifenprodil binding domain on the NR2B protein is crucial for understanding NMDA receptor function.

Purpose of the Study:

• To characterize the structural and functional properties of the ifenprodil binding domain within the amino-terminal domain of the NR2B subunit (ATD2B).
• To elucidate the interactions between critical amino acid residues and ifenprodil in the ATD2B protein.

Main Methods:

• Purification and refolding of soluble recombinant rat NR2B amino-terminal domain (ATD2B).
• Site-directed mutagenesis to alter specific amino acid residues.
• Circular dichroism spectroscopy to assess protein structure and ligand binding.
• Molecular modeling to visualize the ligand binding site.

Main Results:

• Specific binding of ifenprodil to refolded ATD2B was confirmed through spectral measurements.
• Equilibrium constants for ifenprodil and analogues determined by circular dichroism spectroscopy aligned with functional data.
• Mutations at Asp101, Ile150, and Phe176 altered ifenprodil binding affinities, consistent with functional effects.
• Molecular modeling suggested a clam-shell-like structure for ATD2B with critical residues near the binding site.

Conclusions:

• Biochemical measurements confirm that functional assays accurately reflect ligand binding to the ATD of the NR2B subunit.
• This study provides evidence supporting ifenprodil as a direct ligand for the amino-terminal domain of the NR2B subunit.