Compositional versatility enables biologically inspired reverse micelles for study of protein-membrane interactions

Area of Science:

• Biochemistry
• Cell Biology
• Materials Science

Background:

• Understanding cellular membranes and their proteins is crucial for cell biology.
• Current in vitro membrane models lack biological relevance due to differences from actual cell membranes.
• Improved membrane mimetics are needed for accurate studies of membrane-associated proteins.

Purpose of the Study:

• To develop and characterize novel reverse micelle (RM) formulations that mimic specific cellular membrane lipid compositions.
• To determine the upper tolerance concentrations for various lipids within RMs.
• To assess the suitability of these biologically inspired RMs for protein encapsulation and structural studies.

Main Methods:

• Formulation of reverse micelles (RMs) using lipids at molar ratios found in eukaryotic membrane leaflets.
• Characterization of RM formulations using dynamic light scattering (DLS) and cryo-electron microscopy (cryo-EM).
• Encapsulation and analysis of fatty acid binding protein 4 (FABP4) and sterol carrier protein 2 (SCP2) using Nuclear Magnetic Resonance (NMR).

Main Results:

• Established upper tolerance concentrations for lipids in RMs, enabling biologically relevant formulations.
• Created three distinct RM systems (PM-RM, MI-RM, ER-RM) mimicking specific cellular membrane leaflets.
• Demonstrated successful encapsulation of FABP4 and SCP2 within the RMs, confirmed by NMR.
• Achieved the first high-resolution observation of the membrane-bound state of sterol carrier protein 2 (SCP2).

Conclusions:

• The reported RM formulations allow for tailored mimicry of specific cellular membranes.
• These advanced membrane models enhance the study of protein-lipid and protein-membrane interactions.
• This work provides a foundation for more biologically accurate in vitro investigations of membrane proteins.