Energetics of gating MscS by membrane tension in azolectin liposomes and giant spheroplasts

Shaista Shaikh,Charles D Cox,Takeshi Nomura,Boris Martinac

doi:10.4161/chan.28366

Shaista Shaikh, Charles D Cox + Show 2 more

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https://doi.org/10.4161/chan.28366

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Abstract

Mechanosensitive (MS) ion channels are molecular sensors that detect and transduce signals across prokaryotic and eukaryotic cell membranes arising from external mechanical stimuli or osmotic gradients. They play an integral role in mechanosensory responses including touch, hearing, and proprioception by opening or closing in order to facilitate or prevent the flow of ions and organic osmolytes. In this study we use a linear force model of MS channel gating to determine the gating membrane tension (γ) and the gating area change (ΔA) associated with the energetics of MscS channel gating in giant spheroplasts and azolectin liposomes. Analysis of Boltzmann distribution functions describing the dependence of MscS channel gating on membrane tension indicated that the gating area change (ΔA) was the same for MscS channels recorded in both preparations. The comparison of the membrane tension (γ) gating the channel, however, showed a significant difference between the MscS channel activities in these two preparations.

Highlights

Mechanosensitive (MS) ion channels are biological forcesensing systems, which by coupling molecular dynamics of membrane proteins to the mechanics of the surrounding cell membrane convert mechanical stimuli exerted on cellular membranes into electrical or chemical intracellular signals.[1,2,3,4,5] In bacteria, MS channels belonging to the MscL and MscS families protect bacterial cells from hypo-osmotic shock by alleviating osmotic stress.[6]
Analysis of Boltzmann distribution functions describing the dependence of MscS channel gating on membrane tension indicated that the gating area change (ΔA) was the same for MscS channels recorded in both preparations
This was performed by analyzing channel Boltzmann distribution functions, which describe the dependence of channel activity on membrane tension (Fig. 2B)

Summary

Introduction

Mechanosensitive (MS) ion channels are biological forcesensing systems, which by coupling molecular dynamics of membrane proteins to the mechanics of the surrounding cell membrane convert mechanical stimuli exerted on cellular membranes into electrical or chemical intracellular signals.[1,2,3,4,5] In bacteria, MS channels belonging to the MscL and MscS families protect bacterial cells from hypo-osmotic shock by alleviating osmotic stress.[6] The canonical MscS channel of E. coli, is a representative of a very large and diverse family of MS channels found in prokaryotic cells as well as in fungal and plant eukaryotes This channel functions in a weakly hypo-osmotic environment[7,8,9] since it requires less membrane tension to open compared with MscL.[10,11]. In addition to the channel pore seven 14Å portals within the cytoplasmic vestibulum[12,15] control diffusion of ions and solutes across the channel and determine its weak preference for anions over cations.[16,17]

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