An improved open-channel structure of MscL determined from FRET confocal microscopy and simulation.
Mechanosensitive channels act as molecular transducers of mechanical force exerted on the membrane of living cells by opening in response to membrane bilayer deformations occurring in physiological processes such as touch, hearing, blood pressure regulation, and osmoregulation. Here, we determine the likely structure of the open state of the mechanosensitive channel of large conductance using a combination of patch clamp, fluorescence resonance energy transfer (FRET) spectroscopy, data from previous electron paramagnetic resonance experiments, and molecular and Brownian dynamics simulations. We show that structural rearrangements of the protein can be measured in similar conditions as patch clamp recordings while controlling the state of the pore in its natural lipid environment by modifying the lateral pressure distribution via the lipid bilayer. Transition to the open state is less dramatic than previously proposed, while the N terminus remains anchored at the surface of the membrane where it can either guide the tilt of or directly translate membrane tension to the conformation of the pore-lining helix. Combining FRET data obtained in physiological conditions with simulations is likely to be of great value for studying conformational changes in a range of multimeric membrane proteins.
Corry
Ben
B
School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley WA, Australia.
Hurst
Annette C
AC
Pal
Prithwish
P
Nomura
Takeshi
T
Rigby
Paul
P
Martinac
Boris
B
D003198:Computer Simulation; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D040542:Mechanotransduction, Cellular; D018613:Microscopy, Confocal; D008958:Models, Molecular; D017433:Protein Structure, Secondary
D029968:Escherichia coli Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; C086596:MscL protein, E coli