TY - JOUR
T1 - Interaction of the Mechanosensitive Channel, MscS, with the Membrane Bilayer through Lipid Intercalation into Grooves and Pockets
AU - Rasmussen, Tim
AU - Rasmussen, Akiko
AU - Yang, Limin
AU - Kaul, Corinna
AU - Black, Susan
AU - Galbiati, Heloisa
AU - Conway, Stuart J.
AU - Miller, Samantha
AU - Blount, Paul
AU - Booth, Ian Rylance
N1 - Publisher Copyright:
© 2019 The Authors
PY - 2019/8/9
Y1 - 2019/8/9
N2 - 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.
AB - 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.
KW - brominated lipids
KW - electrophysiology
KW - fluorescence quenching
KW - lipid–protein interaction
KW - tension sensing
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U2 - 10.1016/j.jmb.2019.05.043
DO - 10.1016/j.jmb.2019.05.043
M3 - Article
C2 - 31173776
AN - SCOPUS:85067174563
SN - 0022-2836
VL - 431
SP - 3339
EP - 3352
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 17
ER -