Structure-Function Relations of MscS

This chapter discusses the contemporary views on the function, expression, structure, and mechanism of the mechanosensitive channels of small (MscS) proteins. Mechanosensitive (MS) channels in bacterial cells fall into two major categories defined by their core structures: (1) mechanosensitive channels of large (MscL) and (2) MscS. Both channel classes are widespread among bacteria and archaea, and there are also examples found in fungi and plants. Their role in cell physiology is agreednamely, to facilitate the rapid release of solutes in a nondiscriminating manner, such that cytoplasmic turgor is diminished. For both channels, there is an emerging consensus on the structural transitions that they undergo during the opening process. The channels are closed in the growing bacterial cell and that they undergo rapid structural transitions that create transient large pores 8 to 30Ã… diameter. Bacterial cells rely on a selectively permeable membrane to maintain cytoplasmic homeostasis and interconvert energy via ion gradients. The opening of MS channels subverts both of these processes by dispelling ion gradients, lowering the membrane potential, and allowing the nonselective movement of solutes