A thermodynamic and structural study of myelin basic protein in lipid membrane models

Area of Science:

• Biophysics
• Neuroscience
• Materials Science

Background:

• Myelin basic protein (MBP) is crucial for central nervous system myelin sheath structure and function.
• MBP is implicated as an autoantigen in demyelinating diseases like multiple sclerosis.
• The precise structure and lipid interaction mechanisms of MBP within membranes remain unclear.

Purpose of the Study:

• To investigate the interaction of Myelin basic protein (MBP) with model lipid membranes.
• To elucidate the structural and morphological changes induced by MBP in phospholipid Langmuir films.
• To quantify MBP's behavior and partitioning within lipid bilayers under varying surface pressures.

Main Methods:

• Utilized Langmuir films of anionic and neutral phospholipids as model lipid membranes.
• Analyzed surface pressure/area isotherms to determine protein partition coefficients and mixing ratios.
• Employed X-ray reflectivity and Atomic Force Microscopy (AFM) to assess penetration depth and morphology.

Main Results:

• MBP's mixing ratio and molecular area decreased with increasing surface pressure.
• At high surface pressures, MBP preferentially localized at the lipid/water interface for both lipid types.
• AFM revealed MBP forms bean-like structures, inducing lipid compaction and forming scattered protein-lipid complex particles.

Conclusions:

• MBP exhibits complex interactions with lipid membranes, influenced by surface pressure.
• MBP's conformational changes and membrane association are key to its role in myelin structure.
• Understanding these interactions provides insights into demyelinating disease mechanisms.