MECHANOSENSITIVE ION CHANNELS OF ESCHERICHIA-COLI ACTIVATED BY AMPHIPATHS

MECHANOSENSITIVE channels have been found in more than 30 cell types, including bacterial1,2, yeast3, plant4 and animal cells5-9. Whether tension is transferred to the channel through the lipid bilayer and/or underlying cytoskeleton is not clear. Using the patch-clamp method10, we found that amphipathic compounds, which are molecules having hydrophobic and hydrophilic character with positive, negative or no net electric charge at pH7, 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. © 1990 Nature Publishing Group.