  We investigate the possible influence of poly unsaturated fatty acids (PUFAs)
in the lipid bilayer of cell membranes on the conduction properties of the
selectivity filter of voltage gated ion channels. Any change of this
conductivity can have major consequences on electrical signalling in brain and
other cells. At the microscopic level a change in the concentration of PUFAs
can cause a change in the pressure distribution within the lipid bilayer, and
this in turn can lead to a change in the length of the selectivity filter. In
order to estimate the consequences this might entail for the ion channel's
conductivity we performed high resolution molecular dynamics (MD) simulations
of the passage of K+ ions and H2O molecules through the selectivity filter of
the KcsA potassium ion channel. Our results show that a change in length of the
selectivity filter of as little as 4%, independent of whether the filter is
made longer or shorter, will reduce the K+ ion current by around 50%. And
further squeezing or stretching by about 10% can effectively stop the current.
For instructive purposes and to facilitate further interpretation of the
results, we give details of the force models employed in the MD simulations. We
finally discuss the present results in the context of possible effects of
membrane lipid compositions on Kv ion permeation.
