The MscS bacterial mechanosensitive channel family

Mechanosensitive channels (MSCs) are fundamental components of bacterial cells, which function to maintain physical integrity during extreme increases in cell turgor. The MscL and MscS channels are the principal channels involved in this response.  They have been extensively studied at the biochemical, structural and genetic level.  Bacterial strains have multiple MscS family members; E. coli has 6, all homo-heptameric MSCs.  They are related by their common domain structure but are distinguished by the number of proposed transmembrane domains.  We have characterised these 6 channels, demonstrating their electrical activity and function as MSCs.  Physiological consequences of MSC activation depend on multiple channel properties including expression level, conductance, open dwell time, inactivation and additional gating signals.  Abundance and distribution of the MSCs in cell membranes has been measured using western blots and fluorescently-labelled proteins, suggesting an order of magnitude higher than previously thought of mobile channels, which has important implications for understanding MSC function in bacterial cell physiology. We have investigated the gating mechanism and propose a model whereby the number of lipids in pockets between neighbouring subunits determines the closed or open channel state.