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Updated: Jun 1, 2026
Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Published on: May 29, 2011
Using fluorine nuclear magnetic resonance to probe changes in the structure and dynamics of membrane-active peptides
Yuta Suzuki1, Benjamin C Buer, Hashim M Al-Hashimi
1Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
Abstract:
The antimicrobial peptide MSI-78 serves as a model system for studying interactions of bioactive peptides with membranes. Using a series of MSI-78 peptides that incorporate l-4,4,4-trifluoroethylglycine, a small and sensitive (19)F nuclear magnetic resonance probe, we investigated how the local structure and dynamics of the peptide change when it binds to the lipid bilayer. The fluorinated MSI-78 analogues exhibited position-specific changes in (19)F chemical shift ranging from 1.28 to -1.35 ppm upon binding to lipid bicelles. The largest upfield shifts are associated with the most hydrophobic positions in the peptide. Changes in solvent isotope effects (H(2)O/D(2)O) on (19)F chemical shifts were observed for the peptides that are consistent with the MSI-78 solvent-inaccessible hydrophobic core upon binding bicelles. Transverse relaxation measurements of the (19)F nucleus, using the Carr-Purcell-Meiboom-Gill pulse sequence, were used to examine changes in the local mobility of MSI-78 that occur upon binding to the lipid bilayer. Positions in the hydrophobic core of peptide-membrane complex show the greatest decrease in mobility upon binding of the lipid bilayer, whereas residues that interact with lipid headgroups are more mobile. The most mobile positions are at the N- and C-termini of the peptide. These results provide support for the proposed mechanism of membrane disruption by MSI-78 and reveal new details about the dynamic changes that accompany membrane binding.
Insights
Antimicrobial peptide MSI-78
Area of Science:
- Biophysics
- Membrane Biology
- Biochemistry
Background:
- Antimicrobial peptides (AMPs) are crucial for innate immunity.
- MSI-78 is a model antimicrobial peptide for studying peptide-membrane interactions.
- Understanding peptide-membrane dynamics is key to antimicrobial drug development.
Purpose of the Study:
- To investigate local structural and dynamic changes of MSI-78 upon binding to lipid bilayers.
- To utilize fluorine-19 nuclear magnetic resonance ((19)F NMR) as a sensitive probe for these changes.
- To elucidate the mechanism of membrane disruption by MSI-78.
Main Methods:
- Synthesis of MSI-78 analogues incorporating l-4,4,4-trifluoroethylglycine.
- Utilizing (19)F NMR spectroscopy to monitor chemical shift and relaxation.
- Employing solvent isotope effects (H(2)O/D(2)O) to probe hydrophobicity.
- Measuring transverse relaxation rates to assess peptide mobility.
Main Results:
- Position-specific changes in (19)F chemical shifts indicate altered local environments upon bicelle binding.
- Hydrophobic regions of MSI-78 experience significant upfield shifts.
- Reduced mobility observed in the hydrophobic core upon membrane binding.
- N- and C-termini exhibit increased mobility, interacting with lipid headgroups.
Conclusions:
- MSI-78 binding to lipid bilayers induces distinct local structural and dynamic changes.
- The hydrophobic core becomes less mobile, while termini remain flexible.
- These findings support the proposed membrane disruption mechanism of MSI-78.
- Detailed insights into dynamic peptide-membrane interactions are provided.
