Permeation of water through the KcsA K+ channel

Simone Furini, Oliver Beckstein, Carmen Domene Nunez

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Previous studies have reported that the KcsA potassium channel has an osmotic permeability coefficient of 4.8 × 10−12 cm3/s, giving it a significantly higher osmotic permeability coefficient than that of some membrane channels specialized in water transport. This high osmotic permeability is proposed to occur when the channel is depleted of potassium ions, the presence of which slow down the water permeation process. The atomic structure of the potassium-depleted KcsA channel and the mechanisms of water permeation have not been well characterized so far. Here, all-atom molecular dynamics simulations, in conjunction with an umbrella sampling strategy and a nonequilibrium approach to simulate pressure gradients are employed to illustrate the permeation of water in the absence of ions through the KcsA K+ channel. Equilibrium molecular dynamics simulations (95 ns combined total length) identified a possible structure of the potassium-depleted KcsA channel, and umbrella sampling calculations (160 ns combined total length) revealed that this structure is not permeable by water molecules moving along the channel axis. The simulation of a pressure gradient across the channel (30 ns combined total length) identified an alternative permeation pathway with a computed osmotic permeability of ∼(2.7 ± 0.9) × 10−13 cm3/s. Water fluxes along this pathway did not proceed through collective water motions or transitions to vapor state. All of the major results of this study were robust against variations in a wide set of simulation parameters (force field, water model, membrane model, and channel conformation)
Original languageEnglish
Pages (from-to)437-448
Number of pages12
JournalProteins: Structure, Function, and Bioinformatics
Volume74
Issue number2
DOIs
Publication statusPublished - 1 Feb 2009

Keywords

  • osmotic permeability, pressure-induced water transport, liquid vapor oscillations, molecular dynamics, potassium channels, MOLECULAR-DYNAMICS, POTASSIUM CHANNEL, 2.0-ANGSTROM RESOLUTION, MEMBRANE CHANNELS, SIMULATION, ION, AQUAPORINS, SELECTIVITY, CONDUCTION, ENERGETICS

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