Voltage-dependent gating of an asymmetric gramicidin channel.
In an effort to understand the molecular mechanisms of voltage activation of ion channels, we have chosen a system of known structure and examined the properties of heterodimeric channels formed between [Val1]gramicidin A ([Val1]gA) and [F6Val1]gramicidin A ([F6Val1]gA). Gramicidin channels are usually not voltage-dependent; but the introduction of a single symmetry-breaking dipolar F6Val1 residue into a ([Val1]gA)2 dimer to form the [F6Val1]gA/[Val1]gA heterodimer induces voltage-dependent transitions between two conducting states: a high-conductance state and a zero conductance (closed) state. The distribution between these states varies as a function of the applied potential but is not dependent on the nature of the permeant ion (H+ or Cs+). The permeating ions do not seem to contribute to the apparent gating charge.
Oiki
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S
Department of Physiology and Biophysics, Cornell University Medical College, New York, NY 10021.
Koeppe
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RE
Andersen
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OS
D015220:Calcium Channels / Q000502:physiology; D002586:Cesium; D006096:Gramicidin / Q000737:chemistry*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D008564:Membrane Potentials; D008954:Models, Biological; D013329:Structure-Activity Relationship; D014633:Valine
D015220:Calcium Channels; D007473:Ion Channels; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D006096:Gramicidin; D002586:Cesium; D014633:Valine