Professor Boris Martinac
Department of Pharmacology
University of Western Australia
Crawley, Australia

Monday, November 4, 2002
3:00 pm (CT)
3269 Beckman Institute

Abstract

Mechanosensitive (MS) ion channels act as mechano-electrical switches, which open in response to cell membrane deformations. This process is critical to the response of living organisms to direct physical stimulation, as in hearing, touch or osmoregulation. To probe the molecular mechanism of how mechanical force gates MS channels we have recently evaluated two physical mechanisms as triggers of gating of MscL, the bacterial MS channel of large conductance: (i) the energetic cost of protein-lipid bilayer hydrophobic mismatches and (ii) the geometric consequences of bilayer intrinsic curvature. Structural changes in MscL from E. coli were studied using EPR spectroscopy and site-directed spin labeling, whereas the channel function was examined by the patch clamp technique. We have determined the structural rearrangements that underlie MscL closed to open transitions. The open state is highly dynamic, supporting a water-filled pore of at least 25 Å in diameter. Our studies suggest a plausible molecular mechanism of gating in MS channels.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.