The Journal of Membrane Biology

, Volume 131, Issue 3, pp 151–160 | Cite as

Activities of a Mechanosensitive Ion Channel in anE. Coli Mutant Lacking the Major Lipoprotein

  • Andrzej Kubalski
  • Boris Martinact
  • Kit-Yin Ling
  • Julius Adler
  • Ching Kung


The activity of the mechanosensitive (MS) ion channels in membrane patches, excised fromE. coli spheroplasts, was analyzed using the patch-clamp technique. Outer membranes from a mutant lacking the major lipoprotein (Lpp) and its wildtype parent were examined. The MS-channel activities in the wild-type membrane rarely revealed substates at the time resolution used. These channels showed a stretch sensitivity indicated by the IISP (the suction for ane-fold increase in channel open probability) of 4.9 mm Hg suction. The MS-channel activities oflpp included a prominent substate and showed a weaker mechano-sensitivity with an 1/S p of 10.0 mm Hg. Whereas small amphipaths (chlorpromazine, trinitrophenol) or a larger amphipath (lysolecithin) all activated the MS channel in the wild-type membrane under minimal suction, only the larger lysolecithin could activate the MS channel in thelpp membranes. After lysolecithin addition, thelpp membrane became more effective in transmitting the stretch force to the MS channel, as indicated by a steepening of the Boltzmann curve. We discuss one interpretation of these results, in which the major lipoprotein serves as a natural amphipath inserted in the inner monolayer and the loss of this natural amphipath makes the bilayer less able to transmit the gating force.

Key Words

mechanosensitive channel outer membrane Escherichia coli/kw] lipoprotein membrane protein 


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Copyright information

© Springer-Verlag New York Inc 1993

Authors and Affiliations

  • Andrzej Kubalski
    • 1
  • Boris Martinact
    • 1
  • Kit-Yin Ling
    • 1
  • Julius Adler
    • 2
    • 3
  • Ching Kung
    • 1
    • 3
  1. 1.Laboratory of Cell and Molecular BiologyUniversity of WisconsinMadison
  2. 2.Department of BiochemistryUniversity of WisconsinMadison
  3. 3.Department of GeneticsUniversity of WisconsinMadison

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