InterPro domain: IPR006685

This entry represents a family of small conductance mechanosensitive channels (MscS).

Mechanosensitive (MS) channels provide protection against hypo-osmotic shock, responding both to stretching of the cell membrane and to membrane depolarisation. They are present in the membranes of organisms from the three domains of life: bacteria, archaea, and eukarya [ 1 ]. There are two families of MS channels: large-conductance MS channels (MscL) and small-conductance MS channels (MscS or YGGB). The pressure threshold for MscS opening is 50% that of MscL [ 2 ]. The MscS family is much larger and more variable in size and sequence than the MscL family. Much of the diversity in MscS proteins occurs in the size of the transmembrane regions, which ranges from three to eleven transmembrane helices, although the three C-terminal helices are conserved.

MscS folds as a homo-heptamer with a cylindrical shape, and can be divided into transmembrane and extramembrane regions: an N-terminal periplasmic region, a transmembrane region, and a C-terminal cytoplasmic region (middle and C-terminal domains). The transmembrane region forms a channel through the membrane that opens into a chamber enclosed by the extramembrane portion, the latter connecting to the cytoplasm through distinct portals [ 3 ].

In the fission yeast Schizosaccharomyces pombe the mechanosensitive ion channel proteins are known as msy1 and msy2 [ 3 , 4 ].

1. Two families of mechanosensitive channel proteins. Microbiol. Mol. Biol. Rev. 67, 66-85, table of contents
2. Crystal structure of Escherichia coli MscS, a voltage-modulated and mechanosensitive channel. Science 298, 1582-7
3. Organellar mechanosensitive channels in fission yeast regulate the hypo-osmotic shock response. Nat Commun 3, 1020
4. Mechanosensitive channels Msy1 and Msy2 are required for maintaining organelle integrity upon hypoosmotic shock in Schizosaccharomyces pombe. FEMS Yeast Res 14, 992-4