A little bit more about MscS...

Crystal Structure of Escherichia coli MscS, a Voltage-Modulated and Mechanosensitive Channel

Mechanosensitive channels of small conductance are channel proteins that open in response to stretching of the cell and thus help the cell adapt to changes in external osmolarity. The channels open and close due to conformational changes in the protein structure in response to environmental signals such as applied tension. Mechanosensitive channels are also influenced by membrane depolarization and are more likely found to be “open” under such conditions. In this article, the researchers sought to examine the structure of the protein. Mechanosensitive channels have a cylindrical structure and are separated into transmembrane and extramembrane regions. Several arginines are located within the transmembrane channel and cause the channel to be positively charged. This positive charge spanning the channel could explain why the mechanosensitive channels prefer to conduct anions rather than cations. The researchers also looked at the mechanism of the opening and closing of the gate in terms of the protein’s structure. Applied tension results in a change in orientation of certain helices which leads to a change in cross sectional area. This could serve as a sensor between cell tension and conformational changes.

Bass, Randall B., Pavel Strop, Margaret Barclay, and Douglas C. Rees. "Crystal Structure of Escherichia coli MscS, a Voltage-Modulated and Mechanosensitive Channel." Science 298.5598 Nov. (2002): 1582-87.

Concentration dependent effect of GsMTx4 on mechanosensitive channels of small conductance in E. coli spheroplasts

In previous studies it has been found that amphipathic molecules induce the spontaneous closing of mechanosensitive channels of small conductance. However, the mechanisms by which they do so is not fully understood. In this study, the researchers examined the amphipathic peptide GsMTx4 which is found in the venom of tarantulas. GsMTx4 is known to be a specific inhibitor of mechanosensitive channels and the researchers hoped that study of the interactions between the protein and the channel would lead to better understanding of the mechanism by which tension in the membrane leads to structural changes in the channel. The researchers found that GsMTx4 is able to penetrate into the plasma membrane near to the mechanosensitive channel and acts as a gating modifier. The researchers believe that GsMTx4 alters the interactions between the channel protein and the membrane without direct contact with the channel protein itself. Normally during channel opening, the protein undergoes a conformational change in which it thins as it widens with the surrounding lipids in the membrane thinning as well. If GsMTx4 is present nearby to the protein channel, it will disturb this process and the channel will remain closed.

Hurst, AC, PA Gottlieb, and B Martinac. "Concentration dependent effect of GsMTx4 on mechanosensitive channels of small conductance in E. coli spheroplasts." European Biophysics Journal 38.4 Apr. (2009): 415-25. Print.

The Lateral Pressure Profile in Membranes: A Physical Mechanism of General

Anesthesia

This paper suggests that general anesthesia works through the inhibition of protein channels such as the mechanosensitive channel of small conductance. The researchers found that some anesthetics appear to act by incorporating itself into the plasma membrane which results in a change in tension in the membrane. This change in tension in the membrane then leads to a corresponding change in the conformation of the channel protein. An anesthetic will inhibit the channel protein if the conformational change results in a greater cross sectional area in the portion nearest to the aqueous side than the area in the middle of the membrane. However, if the conformational change results in a greater area cross sectional area of the channel protein in the middle of the plasma membrane then the anesthetic is going to increase the channel protein’s activity. 

Cantor, Robert S. "The Lateral Pressure Profile in Membranes: A Physical Mechanism of General Anesthesia." Biochemistry36.94 Mar. (1997): 2339-44.