Whether it is to sense a touch, arterial pressure, or an osmotic gradient across a cell membrane, essentially all living organisms require the ability to detect mechanical force. Electrophysiological evidence has suggested that mechanosensitive ion channels play a major role in many systems where mechanical force is detected. But, despite their biological importance, determination of the most basic structural and functional features of mechanosensitive channels has only recently become possible.
A gene called mscL, originally isolated from Escherichia coli, is the first gene shown to encode a mechanosensitive channel activity. This channel directly responds to tension in the membrane; no other proteins are required. Because of the power of microbial genetics and the availability of structural information (the closed structure was solved to 3.5? resolution), the study of the MscL protein remains, to date, one of the most viable options for understanding the structural and functional characteristics of a mechanosensitive channel.
A major goal of our laboratory is to define the physiological role and molecular mechanisms of MscL and other mechanosensitive channels found in microbes. When assayed by patch clamp, three mechanosensitive channel activities are observed in the inner membrane of E. coli. Studies in other bacteria have demonstrated mechanosensitive channel activity and/or MscL homologues across a vast range of the bacterial kingdom including Gram positive organisms and cyanobacteria. These channels play an important role in osmoregulation by serving as ?emergency release valves? that are triggered upon sudden and severe hypo-osmotic stress. Not only have our studies indicated that bacterial mechanosensitive channels may be valid pharmacological targets for antibacterial agents, but also our findings have given us a first glimpse of the architecture and molecular mechanisms of a channel gated by membrane tension. To study these bacterial mechanosensitive channels we employ a wide variety of approaches including bacterial genetics, whole-cell physiology, molecular and biochemical techniques, and patch clamp of either native bacterial membranes or membrane proteins reconstituted into artificial liposomes.
Recently, our laboratory has also been pursuing a project in which we utilize microbial genetics to study the structure?function relationship of candidate human mechano- and thermal sensors. Although this is a very novel approach, preliminary experiments have shown much promise.
RESEARCH INTERESTS
Mechanosensation
Microbial homeostasis
Osmoregulation
Bacterial channels
mechanosensitive channels
RECENT PUBLICATIONS
Bartlett, J. L., Levin, G, Blount, P., "An in vivo assay identifies changes in residue accessibility on mechanosensitive channel gating" Proc Natl Acad Sci U S A, 101:10161-10165, June 2004
Moe, P. and Blount, P, "Assessment of potential stimuli for mechano-dependent gating of MscL: Effects of pressure, tension, and lipid headgroups." Biochemistry, 44:12239-12244, 2005
Bartlett JL, Li Y, Blount P, "Mechanosensitive channel gating transitions resolved by functional changes upon pore modification." Biophys J, 91:3684-3691, August 2006
Iscla, I., Levin, G., Wray, R., and P. Blount, "Disulfide Trapping the Mechanosensitive Channel MscL into a Gating-Transition State." Biophys J, 92:1224-1232, 2007
Iscla, I., Wray, R., and Paul Blount, "On the Structure of the N-Terminal Domain of the MscL Channel: Helical Bundle or Membrane Interface" Biophys. J., 95:2283-2291, August 2008
SIGNIFICANT PUBLICATIONS
Blount P, Sukharev SI, Moe PC, Martinac B, Kung C, "Mechanosensitive channels of bacteria. Ion Channels, Part C" Methods Enzymol, 294:458-82, 1999
Blount, P., "Molecular Mechanisms of Mechanosensation: Big Lessons from Small Cells" Neuron, 37:731-734, 2003
Kung, C and Blount, P., "Channels in microbes: So many holes to fill" Molecular Microbiology, 53(2):373-380, July 2004
Blount, P., Iscla, I., Moe, P. C., and Li, Y., "The bacterial mechanosensitive channel of large conductance." Mechanosensitive Ion Channels (a volume in the Current Topics in Membranes series), O. P. Hamill, ed. (St. Louis, MO, Elsievier Press), 58:201-233, 2007
Paul Blount, Yuezhou Li, Paul C. Moe, and Irene Iscla HT, "Mechanosensitive Channels Gated by Membrane Tension: Bacteria and Beyond" In: Mechanosensitive ion channels (a volume in the Mechanosensitivity in Cells and Tissues, Moscow Academia series)., New York: Springer Press:71-101, Spring 2008
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