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Mechanosensitive channels allow bacteria to respond to osmotic stress by opening a nanometer-sized pore in the cellular membrane. Although the underlying mechanism has been thoroughly studied on the basis of individual channels, the behavior of channel ensembles has yet to be elucidated. This work reveals that mechanosensitive channels of large conductance (MscL) exhibit a tendency to spatially cluster, and demonstrates the functional relevance of clustering. We evaluated the spatial distribution of channels in a lipid bilayer using patch-clamp electrophysiology, fluorescence and atomic force microscopy, and neutron scattering and reflection techniques, coupled with mathematical modeling of the mechanics of a membrane crowded with proteins. The results indicate that MscL forms clusters under a wide range of conditions. MscL is closely packed within each cluster but is still active and mechanosensitive. However, the channel activity is modulated by the presence of neighboring proteins, indicating membrane-mediated protein-protein interactions. Collectively, these results suggest that MscL self-assembly into channel clusters plays an osmoregulatory functional role in the membrane.

Original publication

DOI

10.1016/j.bpj.2011.01.023

Type

Journal article

Journal

Biophys J

Publication Date

02/03/2011

Volume

100

Pages

1252 - 1260

Keywords

Cell Membrane, Escherichia coli, Escherichia coli Proteins, Ion Channels, Lipid Bilayers, Liposomes, Microscopy, Atomic Force, Neutron Diffraction, Protein Binding, Scattering, Small Angle