MscS ion channel protein structure. Molecular model of a mechanosensitive channel of small conductance (MscS) from an Escherichia coli bacterium. MscSs play a critical role in converting physical stress at the cell membrane into an electrochemical response. They respond to smaller pressures than the large conductance channels. In prokaryotes such as bacteria, such channels open in response to stretch forces in the membrane and help regulate osmotic pressure within the cell by controlling the passage of ions through it.