Structural titration of receptor ion channel GLIC gating by HS-AFM

Gloeobacter violaceus ligand-gated ion channel (GLIC), a proton-gated, cation-selective channel, is a prokaryotic homolog of the pentameric Cys-loop receptor ligand-gated ion channel family. Despite large changes in ion conductance, small conformational changes were detected in X-ray structures of d...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2018-10, Vol.115 (41), p.10333-10338
Main Authors: Ruan, Yi, Kao, Kevin, Lefebvre, Solène, Marchesi, Arin, Corringer, Pierre-Jean, Hite, Richard K., Scheuring, Simon
Format: Article
Language:English
Subjects:
Atomic force microscopy
Bacterial Proteins - chemistry
Bacterial Proteins - metabolism
Biochemistry, Molecular Biology
Biological Sciences
Change detection
Channel gating
Conductance
Cyanobacteria
Cyanobacteria - chemistry
Cysteine Loop Ligand-Gated Ion Channel Receptors - chemistry
Cysteine Loop Ligand-Gated Ion Channel Receptors - metabolism
Homology
Hydrogen-Ion Concentration
Ion Channel Gating - physiology
Ion channels
Ions
Life Sciences
Ligands
Microscopy
Microscopy, Atomic Force - methods
pH effects
Protein Conformation
Protein interaction
Proteins
SEE COMMENTARY
Titration
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Summary:Gloeobacter violaceus ligand-gated ion channel (GLIC), a proton-gated, cation-selective channel, is a prokaryotic homolog of the pentameric Cys-loop receptor ligand-gated ion channel family. Despite large changes in ion conductance, small conformational changes were detected in X-ray structures of detergent-solubilized GLIC at pH 4 (active/desensitized state) and pH 7 (closed state). Here, we used high-speed atomic force microscopy (HS-AFM) combined with a buffer exchange system to perform structural titration experiments to visualize GLIC gating at the single-molecule level under native conditions. Reference-free 2D classification revealed channels in multiple conformational states during pH gating. We find changes of protein–protein interactions so far elusive and conformational dynamics much larger than previously assumed. Asymmetric pentamers populate early stages of activation, which provides evidence for an intermediate preactivated state.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1805621115