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Interaction between ion channel-inactivating peptides and anionic phospholipid vesicles as model targets
J A Encinar1, A M Fernandez, F Gavilanes
1Department of Neurochemistry, University of Alicante, Spain.
Biophysical Journal
|September 1, 1996
Summary
The Shaker B K+ channel peptide binds to anionic vesicles, folds into a beta-structure, and inserts into the bilayer, mimicking channel inactivation. A mutant peptide shows reduced binding and insertion, indicating these steps are crucial for inactivation.
Area of Science:
- Molecular biology
- Biophysics
- Ion channel function
Background:
- Voltage-dependent cation channels undergo rapid inactivation.
- Channel inactivation involves interaction with specific peptide sequences at a hydrophobic vestibule with negative surface potential.
- The Shaker B K+ channel peptide (ShB peptide) is a model for studying inactivation mechanisms.
Purpose of the Study:
- To investigate the interaction of the inactivating ShB peptide and a noninactivating mutant (L7E-ShB) with anionic phospholipid vesicles as a model for the channel inactivation site.
- To elucidate the molecular events underlying channel inactivation by comparing peptide-vesicle interactions with known channel properties.
Main Methods:
- Utilized anionic phospholipid vesicles as a model system mimicking the channel's inactivation entrance.
- Studied the binding affinity, structural changes (beta-structure adoption), and insertion into the vesicle bilayer of both the wild-type ShB peptide and the L7E-ShB mutant peptide.
- Compared the behavior of the inactivating and noninactivating peptides with the model target.
Main Results:
- The inactivating ShB peptide bound with high affinity to anionic vesicles, adopted a beta-structure, and inserted into the hydrophobic bilayer.
- The noninactivating L7E-ShB mutant peptide bound with lower affinity, showed less beta-structure formation, and failed to insert into the vesicle bilayer.
- These differential interactions suggest a correlation between peptide behavior at the vesicle interface and channel inactivation function.
Conclusions:
- Channel inactivation likely involves peptide binding to negatively charged regions, followed by beta-structure folding and insertion into the channel's hydrophobic vestibule.
- The inability of the L7E-ShB mutant to undergo these events explains its lack of channel inactivation.
- Anionic phospholipid vesicles serve as a valid model for studying the molecular mechanisms of ion channel inactivation.