Effect of high hydrostatic pressure on the bacterial mechanosensitive channel MscS.
We have investigated the effect of high hydrostatic pressure on MscS, the bacterial mechanosensitive channel of small conductance. Pressure affected channel kinetics but not conductance. At negative pipette voltages (corresponding to membrane depolarization in the inside-out patch configuration used in our experiments) the channel exhibited a reversible reduction in activity with increasing hydrostatic pressure between 0 and 900 atm (90 MPa) at 23 degrees C. The reduced activity was characterized by a significant reduction in the channel opening probability resulting from a shortening of the channel openings with increasing pressure. Thus high hydrostatic pressure generally favoured channel closing. Cooling the patch by approximately 10 degrees C, intended to order the bilayer component of the patch by an amount similar to that caused by 50 MPa at 23 degrees C, had relatively little effect. This implies that pressure does not affect channel kinetics via bilayer order. Accordingly we postulate that lateral compression of the bilayer, under high hydrostatic pressure, is responsible. These observations also have implications for our understanding of the adaptation of mechanosensitive channels in deep-sea bacteria.
Macdonald
A G
AG
Department of Biomedical Sciences, University of Aberdeen, Aberdeen, AB25 2ZD, UK. a.g.macdonald@abdn.ac.uk
Martinac
B
B
D001703:Biophysics / Q000379:methods*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000502:physiology*; D006874:Hydrostatic Pressure; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry* / Q000502:physiology*; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011312:Pressure; D013104:Spheroplasts / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
D029968:Escherichia coli Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; C469542:MscS protein, E coli