Multiple Mechanosensitive Ion Channels from Escherichia coli,Activated at Different Thresholds of Applied Pressure |
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Authors: | C Berrier M Besnard B Ajouz A Coulombe A Ghazi |
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Institution: | Laboratoire des Biomembranes, URA CNRS 1116, Bat. 432, Université Paris-Sud, 91405 Orsay, France, FR H?pital M. Lannelongue, URA CNRS 1159, 92350 Le Plessis Robinson, France, FR
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Abstract: | Mechanosensitive ion channels from Escherichia coli were studied in giant proteoliposomes reconstituted from an inner membrane fraction, or in giant round cells in which the
outer membrane and the cell wall had been disrupted by a lysozyme-EDTA treatment and a mild osmotic shock. Patch-clamp experiments
revealed the presence in these two preparations of an array of different conductances (100 to 2,300 pS in 0.1 m KCl) activated by stretch. The electrical activity induced by stretch in the native membrane was complex, due to the activation
of several different conductances. In contrast, patches of proteoliposomes generally contained clusters of identical conductances,
which differed from patch to patch. These experiments are consistent with the notion that these different conductances correspond
to different proteins in the plasma membrane of E. coli, which segregate into clusters of identical channels on dilution involved in reconstitution in proteoliposomes. These conductances
could be grouped into three subfamilies of poorly selective channels. In both preparations, the higher the conductance, the
higher was the negative pressure needed for activation. We discuss the putative role of these channels as parts of a multicomponent
osmoregulatory system.
Received: 23 May 1995/Revised: 31 January 1996 |
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Keywords: | : Mechanosensitive ion channels — Escherichia coli— Bacteria — Osmoregulation — Patch-clamp — Liposomes |
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