TOWARDS AN UNDERSTANDING OF THE STRUCTURAL AND FUNCTIONAL-PROPERTIES OF MSCL, A MECHANOSENSITIVE CHANNEL IN BACTERIA

Whether it be to sense a touch, arterial pressure, or an osmotic gradi ent across a cell membrane, essentially all living organisms require t he capability of detecting mechanical force. Electrophysiological evid ence has suggested that mechanosensitive ion channels play a major rol e in many systems where mechanical force is detected. But, despite the ir biological importance, determination of the most basic structural a nd functional features of mechanosensitive channels has only recently become possible. A gene called mscL, which was isolated from Escherich ia coli, was the first gene shown to encode a mechanosensitive channel activity. This channel. directly responds to tension in the membrane; no other proteins are required. MscL appears to be a homohexamer of a 136 amino acid polypeptide that is highly ct helical, contains two tr ansmembrane domains, and has both the amino and carboxyl termini in th e cytoplasm. The study of the MscL protein remains, to date, one of th e most viable options for understanding the structural and functional characteristics of a mechanosensitive channel.