Crystal Structure of <i>Escherichia coli</i> MscS, a Voltage-Modulated and Mechanosensitive Channel

TLDR

The mechanosensitive channel of small conductance (MscS) in *E. coli* responds to membrane stretch and depolarization, and although structurally distinct from other ion channels, its gating mechanisms share common structural elements.

Abstract

The mechanosensitive channel of small conductance (MscS) responds both to stretching of the cell membrane and to membrane depolarization. The crystal structure at 3.9 angstroms resolution demonstrates that Escherichia coli MscS folds as a membrane-spanning heptamer with a large cytoplasmic region. Each subunit contains three transmembrane helices (TM1, -2, and -3), with the TM3 helices lining the pore, while TM1 and TM2, with membrane-embedded arginines, are likely candidates for the tension and voltage sensors. The transmembrane pore, apparently captured in an open state, connects to a large chamber, formed within the cytoplasmic region, that connects to the cytoplasm through openings that may function as molecular filters. Although MscS is likely to be structurally distinct from other ion channels, similarities in gating mechanisms suggest common structural elements.