A three state model for alamethicin conductance in bilayer membranes
Journal of Theoretical Biology
|November 21, 1985
Summary
High pressure significantly slows and alters the conductance onset of the antibiotic alamethicin (a voltage-gated channel former) in lipid membranes, suggesting a multi-step mechanism beyond a simple two-state model.
Area of Science:
- Biophysics
- Membrane Biophysics
- Ion Channel Function
Background:
- Alamethicin forms voltage-gated ion channels in lipid bilayers.
- Previous studies indicated pressure affects alamethicin channel kinetics.
Purpose of the Study:
- Investigate the pressure dependence of alamethicin conductance.
- Elucidate the mechanism of alamethicin channel gating under pressure.
Main Methods:
- Applied voltage steps to lipid bilayers containing alamethicin at varying pressures (up to 100 MPa).
- Measured changes in alamethicin conductance over time.
- Analyzed kinetic parameters of conductance onset and decay.
Main Results:
- High pressure (100 MPa) markedly slowed alamethicin conductance onset.
- Conductance onset became sigmoidal at elevated pressures, unlike the response at ambient pressure.
- Conductance decay remained single exponential but was also pressure-dependent.
- Kinetic parameters for onset and decay exhibited distinct pressure dependencies.
Conclusions:
- A simple two-state model cannot explain the observed pressure-dependent kinetics.
- A three-state model involving surface and precursor states is proposed to account for the sigmoidal onset.
- The findings provide insights into the complex gating mechanism of alamethicin channels.
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