The small mechanosensitive channel, MscS, is a part of the turgor-driven solute efflux system that protects bacteria from lysis in the event of osmotic shock. The MscS protein alone is sufficient to form a functional mechanosensitive channel gated directly by tension in the lipid bilayer. The MscS proteins are heptamers of three transmembrane subunits with seven converging M3 domains, and this MscS_porin is towards the N-terminal of the molecules. The high concentration of negative charges at the extracellular entrance of the pore helps select the cations for efflux.

1: Protection of Escherichia coli cells against extreme turgor by activation of MscS and MscL mechanosensitive channels: identification of genes required for MscS activity. Levina N, Totemeyer S, Stokes NR, Louis P, Jones MA, Booth IR; EMBO J. 1999;18:1730-1737. PMID:10202137

2: Purification of the small mechanosensitive channel of Escherichia coli (MscS): the subunit structure, conduction, and gating characteristics in liposomes. Sukharev S; Biophys J. 2002;83:290-298. PMID:12080120

3: A possible unifying principle for mechanosensation. Kung C; Nature. 2005;436:647-654. PMID:16079835