抄録
Mechanosensation is involved in various biological responses such as hearing, gravity perception, and osmoregulation. The membrane excitation on cell deformation is mainly brought about mechanosensitive channels. Two types of mechanosensitive channels have been identified: one that is directly activated by membrane tension and the other that detects stress through the linkage between extracellular and intracellular components. Bacterial mechanosensitive channels, MscL and MscS, belong the former type. In fact, incorporation of amphypath or lisophosphatidylcholine increases the mechanosensitivity of MscS and MscL. Random mutagenesis study indicates that hydrophobic interaction between the residues in the transmembrane domain and the lipid is essential for the mechanosensitivity. Scanning mutagenesis in which the hydrophobic interaction is interfered by asparagine substitution indicates that hydrophobic residues at the periplasmic ends of the transmembrane α helices of MscL are important for mechanosensing. Similar approach on MscS revealed that both ends of the transmembrane α helices have a interaction essential to the mechanosensitivity. These findings are consistent with the idea of the lateral pressure profile of the lipid bilayer, which suggests that membrane protein is subject to negative pressure only near the surface of the bilayer. Therefore, the hydrophobic residues identified at the ends of transmembrane α helices probably receive the force from the lipid and form the mechanosensor of MscS and MscL. [Jpn J Physiol 55 Suppl:S12 (2005)]
