Mechanosensitive channels in prokaryotes

Compared to voltage-dependent or ligand-gated ion channels that have extens ively been studied over the last twenty years, there is little knowledge av ailable on structure and function of mechanosensitive (MS) channels that co nstitute the third major group of ion channels classified according to thei r gating mechanism. The main purpose of this review is to summarize an area of the MS channel research where major progress has occurred. Cloning of M scL and MscS, the MS channels of large and Small conductance found in Bacte ria and elucidation of the 3D crystal structure of MscL are discussed in co njunction with the physiological role of the MS channels in bacterial osmor egulation. Furthermore, cloning and molecular characterization of MS channe ls in Archaea Methanococcus jannashii and Thermoplasma acidophilum are desc ribed. They present examples of the recent promising developments, which ma y ultimately lead to the understanding of the biophysical principles and ev olutionary origins of mechanosensory transduction. Although they conduct io ns and are usually characterized by their ionic conductance and selectivity , the MS channels in prokaryotes may primarily serve to transport osmotican ts other than ions. Therefore, throughout this review prokaryotic MS ion ch annels are referred to as MS channels rather than MS ion channels. Copyrigh t (C) 2001 S. Karger AG, Basel.