Yong Wang, Yanxin Liu, Hannah A. DeBerg, Takeshi Nomura, Melinda Tonks Hoffman,
Paul R. Rohde, Klaus Schulten, Boris Martinac, and Paul R. Selvin.
Single molecule FRET reveals pore size and opening mechanism of
MscL.
eLife, 3:e01834, 2014.
(21 pages).
WANG2014
The mechanosensitive channel of large conductance, which serves as a model system for
mechanosensitive channels, has previously been crystallized in the closed form, but not in
the open form. Ensemble measurements and electrophysiological sieving experiments
show that the open-diameter of the channel pore is >25 Å, but the exact size
and whether the conformational change follows a helix-tilt or barrel-stave model are
unclear. Here we report measurements of the distance changes on liposome-reconstituted
MscL transmembrane -helices, using a ``virtual sorting" single-molecule
fluorescence energy transfer. We observed directly that the channel opens via the helix-tilt
model and the open pore reaches 2.8 nm in diameter. In addition, based on the
measurements, we developed a molecular dynamics model of the channel structure in the
open state which confirms our direct observations.
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