Peptoid-based macrodiscs of variable lipid composition for structural studies of membrane proteins by oriented-sample...

Area of Science:

• Biophysics
• Structural Biology
• Membrane Protein Research

Background:

• Solid-state Nuclear Magnetic Resonance (NMR) is crucial for membrane protein structure determination.
• Discoidal lipid mimics provide planar bilayer environments for NMR studies.
• Previous peptoid-based macrodiscs showed promise but required improvement.

Purpose of the Study:

• To enhance magnetic alignment and NMR resolution of peptoid-based macrodiscs.
• To investigate the impact of lipid composition on macrodisc properties.
• To explore detergent-free macrodisc formation with different lipids.

Main Methods:

• Utilizing solid-state NMR spectroscopy.
• Employing magnetically aligned discoidal lipid macrodiscs.
• Comparing DMPC/DMPG (85:15) and DPPC lipid compositions.

Main Results:

• A mixture of DMPC/DMPG lipids significantly improved magnetic alignment and NMR resolution (30% sharper linewidths).
• Higher orientational order parameter observed, likely due to electrostatic repulsion.
• Detergent-free macrodiscs successfully formed using DPPC lipids.
• Pf1 spectra were similar across different lipid mimetics, suggesting other factors influence helix tilt.

Conclusions:

• Modified peptoid-based macrodiscs offer superior alignment and resolution for membrane protein NMR.
• Lipid composition, including charge and chain length, critically affects macrodisc performance.
• Transmembrane helix tilt may be influenced by both hydrophobic matching and interfacial residue interactions.