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The ability of proteins to sense membrane tension is pervasive in biology. A higher-resolution structure of the Escherichia coli small-conductance mechanosensitive channel MscS identifies alkyl chains inside pockets formed by the transmembrane helices (TMs). Purified MscS contains E. coli lipids, and fluorescence quenching demonstrates that phospholipid acyl chains exchange between bilayer and TM pockets. Molecular dynamics and biophysical analyses show that the volume of the pockets and thus the number of lipid acyl chains within them decreases upon channel opening. Phospholipids with one acyl chain per head group (lysolipids) displace normal phospholipids (with two acyl chains) from MscS pockets and trigger channel opening. We propose that the extent of acyl-chain interdigitation in these pockets determines the conformation of MscS. When interdigitation is perturbed by increased membrane tension or by lysolipids, the closed state becomes unstable, and the channel gates.

Original publication

DOI

10.1038/nsmb.3120

Type

Journal article

Journal

Nat Struct Mol Biol

Publication Date

12/2015

Volume

22

Pages

991 - 998

Keywords

Biophysical Phenomena, Crystallography, X-Ray, Escherichia coli, Escherichia coli Proteins, Ion Channels, Mechanotransduction, Cellular, Models, Molecular, Molecular Dynamics Simulation, Phospholipids, Protein Conformation