Voltage sensing in ion channels: Mesoscale simulations of biological devices

Alexander Peyser and Wolfgang Nonner
Phys. Rev. E 86, 011910 – Published 11 July 2012
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Abstract

Electrical signaling via voltage-gated ion channels depends upon the function of a voltage sensor (VS), identified with the S1–S4 domain in voltage-gated K+ channels. Here we investigate some energetic aspects of the sliding-helix model of the VS using simulations based on VS charges, linear dielectrics, and whole-body motion. Model electrostatics in voltage-clamped boundary conditions are solved using a boundary element method. The statistical mechanical consequences of the electrostatic configurational energy are computed to gain insight into the sliding-helix mechanism and to predict experimentally measured ensemble properties such as gating charge displaced by an applied voltage. Those consequences and ensemble properties are investigated for two alternate S4 configurations, α and 310 helical. Both forms of VS are found to have an inherent electrostatic stability. Maximal charge displacement is limited by geometry, specifically the range of movement where S4 charges and countercharges overlap in the region of weak dielectric. Charge displacement responds more steeply to voltage in the α-helical than in the 310-helical sensor. This difference is due to differences on the order of 0.1 eV in the landscapes of electrostatic energy. As a step toward integrating these VS models into a full-channel model, we include a hypothetical external load in the Hamiltonian of the system and analyze the energetic input-output relation of the VS.

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  • Received 7 February 2012

DOI:https://doi.org/10.1103/PhysRevE.86.011910

©2012 American Physical Society

Authors & Affiliations

Alexander Peyser

  • Department of Physiology and Biophysics, University of Miami, Coral Gables, Florida 33146, USA and Computational Biophysics, German Research School for Simulation Sciences, 52425 Jülich, Germany

Wolfgang Nonner*

  • Department of Physiology and Biophysics, University of Miami, Coral Gables, Florida 33146, USA

  • *wnonner@med.miami.edu

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Issue

Vol. 86, Iss. 1 — July 2012

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