Mechanosensitive channels in microbes.
All cells, including microbes, detect and respond to mechanical forces, of which osmotic pressure is most ancient and universal. Channel proteins have evolved such that they can be directly stretched open when the membrane is under turgor pressure. Osmotic downshock, as in rain, opens bacterial mechanosensitive (MS) channels to jettison osmolytes, relieving pressure and preventing cell lysis. The ion flux through individual channel proteins can be observed directly with a patch clamp. MS channels of large and small conductance (MscL and MscS, respectively) have been cloned, crystallized, and subjected to biophysical and genetic analyses in depth. They are now models to scrutinize how membrane forces direct protein conformational changes. Eukaryotic microbes have homologs from animal sensory channels of the TRP superfamily. The MS channel in yeast is also directly sensitive to membrane stretch. This review examines the key concept that proteins embedded in the lipid bilayer can respond to the changes in the mechanical environment the lipid bilayer provides.
Kung
Ching
C
Laboratory of Molecular Biology and Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA. ckung@wisc.edu
Martinac
Boris
B
Sukharev
Sergei
S
D001419:Bacteria / Q000378:metabolism; D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D040542:Mechanotransduction, Cellular; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D017386:Sequence Homology, Amino Acid; D013314:Stress, Mechanical; D015003:Yeasts / Q000378:metabolism / Q000502:physiology*
D001426:Bacterial Proteins; D005656:Fungal Proteins; D026901:Membrane Transport Proteins