Marcos Sotomayor and Klaus Schulten.
Molecular dynamics study of gating in the mechanosensitive channel of
small conductance MscS.
Biophysical Journal, 87:3050-3065, 2004.
(PMC: 1304777)
SOTO2004
Mechanosensitive channels are a class of ubiquitous membrane proteins
gated by mechanical strain in the cellular membrane.
MscS, the mechanosensitive channel of small conductance, is found in the
inner membrane of E. coli and its crystallographic structure in an
open form has been recently solved. By means of molecular dynamics simulations we studied the stability
of the channel conformation suggested by crystallography in a fully
solvated lipid (POPC) bilayer, the combined system encompassing 224,340
atoms. When restraining the backbone of the protein, the channel
remained in the open form and the simulation
revealed intermittent permeation of water molecules through the channel.
Abolishing the restraints under constant pressure conditions lead to
spontaneous closure of the transmembrane channel, while abolishing
the restraints when surface tension (20 dyn/cm) was applied lead to
channel widening. The large balloon-shaped cytoplasmic domain of
MscS exhibited spontaneous diffusion of ions through its side openings.
Interaction between the transmembrane domain and the cytoplasmic
domain of MscS was observed and involved formation of salt bridges between
residues ASP62 and ARG128; this interaction may be essential for the gating of
MscS. K and Cl ions showed distinctively different distributions in
and around the channel.
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and Cl
ions showed distinctively different distributions in
and around the channel.
