Gramicidin channels are internally gated.
Tyson L Jones1, Riqiang Fu, Frederick Nielson
1Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah, USA.
Biophysical Journal
|April 23, 2010
Summary
Gramicidin channels do not dissociate when conductance stops. Instead, stable conformational changes in monomers likely gate channel activity, as revealed by solid-state NMR.
Area of Science:
- Biophysics
- Structural Biology
- Membrane Proteins
Background:
- Gramicidin channels are model systems for solid-state NMR and single-channel conductance studies.
- Previous multichannel studies suggested conductance changes result from monomer-dimer reactions.
Purpose of the Study:
- To investigate the molecular mechanisms underlying gramicidin channel gating.
- To determine if gramicidin channels dissociate upon conductance termination.
Main Methods:
- Single-molecule deposition using vesicle fusion to a planar bilayer.
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
- Two-dimensional chemical exchange NMR.
Main Results:
- Gramicidin dimer channels were shown not to dissociate when conductance terminated.
- Solid-state NMR revealed two stable monomer conformations.
- Slow conformational exchange (lifetimes of seconds) was observed for Val1 carbonyls.
Conclusions:
- Gramicidin channel gating is likely regulated by small conformational changes near the permeation pathway, not dissociation.
- These findings provide molecular-level insights into channel gating mechanisms.
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