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Modeling negative ion defect migration through the gramicidin A channel
Alexander V Nemukhin1, Ilya A Kaliman, Alexander A Moskovsky
1Department of Chemistry, M.V. Lomonosov Moscow State University, 1/3 Leninskie Gory, Moscow, 119992, Russian Federation. anem@lcc.chem.msu.ru
Journal of Molecular Modeling
|February 10, 2009
Summary
This study explores proton conduction in gramicidin A, revealing that negative ion defect migration is a viable mechanism. This finding suggests a new pathway that may compete with water reorientation in limiting proton transport.
Area of Science:
- Biophysics
- Computational Biology
- Ion Channels
Background:
- Gramicidin A channels facilitate proton transport across cell membranes.
- The precise mechanisms of proton conduction, including rate-limiting steps, are still under investigation.
Purpose of the Study:
- To investigate proton conduction mechanisms in gramicidin A using potential of mean force (PMF) calculations.
- To evaluate the role of negative ion defect migration as a potential mechanism for proton conduction.
Main Methods:
- Molecular dynamics simulations utilizing CHARMM/PM6/TIP3P parameters.
- Potential of mean force (PMF) calculations to determine energy landscapes.
- Modeling of gramicidin A channel with internal water molecules and external water clusters.
Main Results:
- Proton migration and water reorientation energies are consistent with previous studies.
- Calculated energy for negative ion defect migration (3.8 kcal mol⁻¹) is comparable to water reorientation energy (5.4 kcal mol⁻¹).
- Negative ion defect migration was simulated for the first time in molecular dynamics.
Conclusions:
- Negative ion defect migration is a plausible mechanism for proton conduction in gramicidin A.
- This mechanism may compete with water reorientation as the rate-limiting step in proton transport.
- The findings provide new insights into the molecular basis of proton transport through ion channels.
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