Interaction of the Mechanosensitive Channel, MscS, with the Membrane Bilayer through Lipid Intercalation into Grooves and Pockets

Tim Rasmussen, Akiko Rasmussen, Limin Yang, Corinna Kaul, Susan Black, Heloisa Galbiati, Stuart J. Conway, Samantha Miller, Paul Blount, Ian Rylance Booth

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

All membrane proteins have dynamic and intimate relationships with the lipids of the bilayer that may determine their activity. Mechanosensitive channels sense tension through their interaction with the lipids of the membrane. We have proposed a mechanism for the bacterial channel of small conductance, MscS, that envisages variable occupancy of pockets in the channel by lipid chains. Here, we analyze protein–lipid interactions for MscS by quenching of tryptophan fluorescence with brominated lipids. By this strategy, we define the limits of the bilayer for TM1, which is the most lipid exposed helix of this protein. In addition, we show that residues deep in the pockets, created by the oligomeric assembly, interact with lipid chains. On the cytoplasmic side, lipids penetrate as far as the pore-lining helices and lipid molecules can align along TM3b perpendicular to lipids in the bilayer. Cardiolipin, free fatty acids, and branched lipids can access the pockets where the latter have a distinct effect on function. Cholesterol is excluded from the pockets. We demonstrate that introduction of hydrophilic residues into TM3b severely impairs channel function and that even “conservative” hydrophobic substitutions can modulate the stability of the open pore. The data provide important insights into the interactions between phospholipids and MscS and are discussed in the light of recent developments in the study of Piezo1 and TrpV4.

Original languageEnglish (US)
Pages (from-to)3339-3352
Number of pages14
JournalJournal of Molecular Biology
Volume431
Issue number17
DOIs
StatePublished - Aug 9 2019

Keywords

  • brominated lipids
  • electrophysiology
  • fluorescence quenching
  • lipid–protein interaction
  • tension sensing

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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