Mechanosensitive channel that opens in response to membrane tension and specific ionic conditions. Requires high concentrations of external K(+), NH(4)(+), Rb(+) or Cs(+) to gate. May participate in the regulation of osmotic pressure changes within the cell, although it does not appear to have a major role in osmolarity regulation. Forms an ion channel of 1.0 nanosiemens conductance. The channel can remain active for between 30 seconds and over 3 minutes; it does not desensitize upon extended pressure. Its activity is masked in wild-type cells by the MscS channel. Belongs to the MscS (TC 1.A.23) family.