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Hierarchical approach to predicting permeation in ion channels
R J Mashl1, Y Tang, J Schnitzer
1Beckman Institute for Advanced Science and Technology, Department of Molecular and Integrative Physiology, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801, USA. mashl@ncsa.uiuc.edu
Biophysical Journal
|October 19, 2001
Summary
This study presents a computational method to simulate KcsA potassium channel function, accurately predicting ion flow and channel properties. The approach integrates multiple simulation techniques for reliable ion channel behavior prediction.
Area of Science:
- Biophysics
- Computational Biology
- Structural Biology
Background:
- The KcsA potassium channel's function is crucial for cellular electrophysiology.
- Understanding ion permeation mechanisms requires integrating structural and dynamic information.
Purpose of the Study:
- To develop and validate a hierarchical computational strategy for predicting electrophysiologically measurable properties of the KcsA potassium channel.
- To investigate K(+) ion permeation mechanisms and channel gating using a multi-scale simulation approach.
Main Methods:
- Hierarchical computational strategy combining molecular modeling, electrostatics, molecular dynamics, and Brownian dynamics simulations.
- Development of KcsA channel models with varying pore sizes based on X-ray structures and experimental gating data.
- Incorporation of pH-dependent gating into ion potential profiles and combining with molecular dynamics-derived ion mobilities for Brownian dynamics simulations.
Main Results:
- Simulated conductance of ~110 pS under 250 mM K(+) conditions, aligning with experimental data for the largest substate.
- Channel dimensions consistent with electrophysiologically determined ion blocking and structural evidence of quaternary ammonium ion permeation.
- Obtained realistic values for ion distribution, flux ratios, and current-voltage/concentration curves.
- Brownian dynamics suggest a three-ion 'knock-off' mechanism for ion passage through the selectivity filter.
Conclusions:
- The integrated computational approach accurately captures K(+) ion permeation in the KcsA channel.
- This study provides a proof-of-concept for predicting ion channel function from structure using a multi-tiered approach.
- The methodology is applicable to predicting the function of other ion channel structures.