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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
68
8-POS
Board 8
Brownian Dynamics Study of Permeation and Selectivity of NaChBac and Its Mutants
Miraslau L. Barabash
1
, Dmitry G. Luchinsky
1,2
, William Gibby
1
, Carlo Guardiani
3
, Olena A.
Fedorenko
4
, Stephen K. Roberts
4
, Peter McClintock
1
.
1
Department of Physics, Lancaster University, LA1 4YB, Lancaster, Lancashire, United
Kingdom,
2
SGT Inc., Greenbelt 20770, MD, USA,
3
School of Engineering, University of
Warwick, CV4 7AL, Coventry, Warwickshire, United Kingdom,
4
Division of Biomedical and
Life Sciences, Lancaster University, LA1 4YG, Lancaster, Lancashire, United Kingdom.
We study the permeation and selectivity of NaChBac, a bacterial tetramer channel, using
Brownian dynamics (BD) simulations. The molecular structure of the selectivity filter (SF) has
been reconstructed in simulations recently [1], and thus our present study links this structure with
newly found experimental properties of the channel and its mutants [2].
We use BD to describe ionic motion through the SF, where the injection of ions is implemented
via the Grand Canonical Monte-Carlo scheme [3]. We apply the single-ion potentials of mean
force (PMFs), which are obtained from the molecular dynamics (MD) simulations [4, 5] thus
reflecting the structure of the channel protein. Ion-ion interactions are modelled via screened
Coulomb interactions. The model reproduces the electric current and spatial distribution of ions,
which are compared with experimental recordings of conduction and selectivity in the NaChBac
wild-type channel (LESWAS) and its mutants, LEDWAS, and LDDWAD [2]. The selectivity
between Na and K ions is found to arise from different PMFs seen by these ions, with a non-
monotonous current-concentration curve when the particle solutions contain both Na and K ions.
We believe the results can find application in physiology, as well as in artificial nanopores and
nanoscale fluid filters. The research was partially supported by the Engineering and Physical
Sciences Research Council UK (grant No. EP/M015831/1).
1. C. Guardiani et al., J. Chem. Theory Comput. 13 (3), pp 1389–1400 (2017)
2. O.A. Fedorenko, S.K. Roberts (in preparation)
3. W. Im et al., Biophys J. 79(2): 788–801 (2000)
4. M.A. Wilson, T.H. Nguyen, A. Pohorille, J. Chem .Phys. 141, 22D519 (2014)
5. C. Guardiani et al. (in preparation)