Influence Of The Lipid-Protein Interface On Mscs Mechanosensitive Channel Gating At High Resolutions

Prokaryotic mechanosensitive (MS) channels gate by sensing forces through interactions with the lipid bilayer. This points to a critical role of lipid-protein interface in defining force-from-lipid gating, and defining the specific structural and energetic interplay between channels and the lipids that surround them represents a fundamental challenge in mechanobiology. Recently, we have determined several high resolution cryo-EM structures of MscS (the small-conductance mechanosensitive channel) in nanodisc (ND) environments that varied membrane composition. Surprisingly, the bulk of the ND-containing lipid annulus surrounding the channel was found to be almost a full bilayer leaflet towards the N-terminal where previous expected. Furthermore, several lipids were identified within these close conformation structures which, we hypothesize, play a critical role in channel gating. We have expanded on these new structures by probing the function of the interacting lipids which varied a number of membrane properties, including membrane thickness, overall charge, size, and membrane rigidity. These observations were further evaluated by several functional and biochemical assays, including crosslinking assays, down shock cell survival and high speed pressure clamp electrophysiology. The present observations redefine the mechanism of force-from-lipids gating and suggest that allosteric interactions between TM and coordinating lipids segments play a fundamental role in MscS gating.