Mechanosensitive ion channels of E. coli activated by amphipaths.
Mechanosensitive channels have been found in more than 30 cell types, including bacterial, yeast, plant and animal cells. Whether tension is transferred to the channel through the lipid bilayer and/or underlying cytoskeleton is not clear. Using the patch-clamp method, we found that amphipathic compounds, which are molecules having hydrophobic and hydrophilic character with positive, negative or no net electric charge at pH 7, could slowly activate the mechanosensitive channels of giant Escherichia coli spheroplasts, with effectiveness proportional to their lipid solubility. The cationic or anionic amphipaths were able to compensate for each other's effect. After a channel was activated by an amphipath of one charge, if that amphipath was gradually replaced by one with the opposite charge, the channel first inactivated before reactivating. These findings support the view that the mechanical gating force can come from the surrounding lipids.
Laboratory of Molecular Biology, University of Wisconsin, Madison 53706.
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Martinac
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Adler
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Kung
D002462:Cell Membrane / Q000502:physiology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002746:Chlorpromazine / Q000494:pharmacology; D004563:Electrochemistry; D004926:Escherichia coli / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008563:Membrane Lipids; D010851:Picrates / Q000494:pharmacology; D012995:Solubility
D007473:Ion Channels; D008563:Membrane Lipids; D010851:Picrates; C005858:picric acid; D002746:Chlorpromazine