The Supercomputer as Virtual Cell
Conduction in Ion Channels: The Molecular Mechanism
The regulation and transduction of signals between cells and their environment are mediated in
many cases by channels and pores residing in cell membranes. They are an important class of
biomolecular machines. They work by selecting specific ions and by catalyzing the passive
diffusion through the selectivity filter. The picture shows the potassium
channel KcsA residing
inside a lipid membrane surrounded by water molecules. Controlled molecular dynamics
simulations were conducted with this model system that consists of about
30,000 atoms. The
simulations permit the collective motion of ions and water molecules to
be monitored through the
narrow selectivity filter. The simulations reveal that the high conductivity is based on the
cooperative diffusion of ions and water molecules mediated by the flexible carbonyl groups
lining the selectivity filter. The schematic diagram on the right hand
side shows four successive
configurations of ions and water molecules passing through the filter.
(Jean-Fang Gwan, Artur Baumgärtner, Institute of
Solid State Research, Research Center Jülich)
Sabine Höfler-Thierfeldt