Self-assembled lipid and membrane protein polyhedral nanoparticles

Area of Science:

• Structural Biology
• Nanotechnology
• Biophysics

Background:

• Membrane proteins are crucial for cellular functions but challenging to analyze structurally.
• Existing methods often struggle to maintain native protein conformations.

Purpose of the Study:

• To develop a novel method for self-assembly of membrane proteins into nanoparticle structures.
• To enable high-resolution structural determination of membrane proteins in a lipidic environment.
• To explore potential applications of these nanoparticles.

Main Methods:

• Self-assembly of membrane proteins and phospholipids into polyhedral nanoparticles (MPPNs).
• Utilized Escherichia coli mechanosensitive channel of small conductance (MscS) as a model.
• Electron cryotomography and single-particle electron cryomicroscopy for structural analysis.
• Microfluidics-based free interface diffusion system for MPPN preparation.

Main Results:

• MPPNs with uniform radii (∼20 nm) were successfully prepared.
• Electron cryotomography revealed 24 MscS heptamers with octahedral symmetry.
• Single-particle electron cryomicroscopy achieved ∼1-nm resolution, showing a nonconducting state.
• Demonstrated generality by preparing MPPNs for other membrane proteins (MscL, Cx26).

Conclusions:

• MPPNs offer a robust platform for membrane protein structural analysis in a native-like environment.
• The closed surface of MPPNs facilitates studies under physiological transmembrane gradients.
• MPPNs show promise for drug delivery and inorganic nanoparticle templating.