Voltage modulation of MscL channel reconstituted in artificial liposomes

The large conductance mechanosensitive channel (MscL) of E. coli has been widely studied as the prototype ion channel gated by mechanical stress. It detects membrane tension and acts as a safety valve, paramount for the survival of the bacterium when subjected to hypo-osmotic stress. The MscL channel was reconstituted in azolectin liposomes. In excised patches corresponding to the inside-out mode and symmetrical solutions consisting of 200 mM KCl and 40mM MgCl2, the channel was activated with suction (40 mm to 100 mm Hg) applied to the recording pipette. Its conductance was measured at ~ 3nS and the steady-state open probability closely followed a Boltzmann distribution curve. However the channel could also be modulated by voltage, with a higher opening probability at negative pipette potentials. Unlike the mechanosensitive channel of small conductance (MscS), with a putative voltage sensor composed of arginine residues in the first and second transmembrane domains, MscL has no such identifiable voltage sensor. It is postulated that the observed voltage modulation may be the indirect result of changes in bilayer tension induced by voltage. Supported by the Australian Research Council