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Distinguishing bicontinuous lipid cubic phases from isotropic membrane morphologies using (31)P solid-state NMR
Yu Yang1, Hongwei Yao1, Mei Hong1
1Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States.
The Journal of Physical Chemistry. B
|March 28, 2015
Summary
Nuclear Magnetic Resonance (NMR) can now identify lipid cubic phases, crucial for understanding protein-induced membrane changes. This new NMR method reveals viral fusion proteins induce specific membrane curvatures, impacting virus-cell fusion mechanisms.
Area of Science:
- Membrane biophysics
- Structural biology
- Biophysical chemistry
Background:
- Proteins that fuse, bend, and cut membranes induce nonlamellar lipid membrane structures.
- Hexagonal and lamellar phases are identifiable via solid-state NMR, but bicontinuous lipid cubic phases are not.
- Small-angle X-ray scattering is the current standard for identifying cubic phases.
Purpose of the Study:
- To develop a novel NMR-based method for identifying lipid cubic phases.
- To investigate the unique NMR signatures of lipid cubic phases.
- To explore the role of viral fusion proteins in inducing membrane curvature.
Main Methods:
- Simulated (31)P chemical shift line shapes of oriented cubic-phase membranes.
- Measured (31)P T2 relaxation times to differentiate between micelles and cubic phases.
- Applied the NMR relaxation approach to a DOPE membrane with a viral fusion protein transmembrane domain (TMD).
Main Results:
- Lipid cubic phases exhibit significantly shorter (31)P T2 relaxation times compared to isotropic micelles.
- The viral fusion protein TMD was shown to induce negative Gaussian curvature in DOPE membranes, characteristic of cubic phases.
- The observed (31)P spectrum and T2 relaxation times of the DOPE membrane indicated the formation of a cubic phase.
Conclusions:
- A simple NMR diagnostic probe for lipid cubic phases has been established.
- This NMR method can distinguish cubic phases from isotropic membrane morphologies.
- The findings provide insights into protein-induced membrane remodeling and virus-cell fusion mechanisms.
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