Membrane proteins in reverse micelles: myelin basic protein in a membrane-mimetic environment

Area of Science:

• Biochemistry
• Biophysics
• Neuroscience

Background:

• Myelin basic protein (MBP) is crucial for myelin sheath structure and function.
• Understanding MBP's behavior in membrane-mimetic environments is key to elucidating its role in demyelinating diseases.

Purpose of the Study:

• To investigate the solubility, reactivity, and conformational dynamics of bovine MBP in AOT reverse micelles.
• To characterize the membrane-mimetic properties of the AOT-isooctane-water system for MBP.

Main Methods:

• Solubility studies of MBP in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles.
• Conformational analysis using techniques sensitive to protein folding (e.g., alpha-helix content).
• Reactivity assays (o-phthalaldehyde, N-bromosuccinimide) to probe solvent accessibility of protein residues.

Main Results:

• MBP exhibits optimal solubility in AOT reverse micelles at a lower water-to-surfactant ratio ([H2O]/[AOT] = w0) than other water-soluble proteins.
• MBP transitions from an unfolded state in aqueous solution to a more folded conformation (20% alpha-helix) in reverse micelles, independent of w0.
• Specific residues are accessible to solvent, while the tryptophan residue (Trp-117) is shielded.

Conclusions:

• AOT reverse micelles provide a suitable membrane-mimetic environment for studying MBP.
• MBP's conformational stability and specific residue accessibility are modulated by the reverse micelle system.
• These findings offer insights into MBP's interactions within the myelin sheath.