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Cooperative Gating of a K+ Channel by Unmodified Biological Anionic Lipids Viewed by Solid-State NMR Spectroscopy
Maryam Yekefallah1, Evan J van Aalst1, Roy A M van Beekveld2
1Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States.
Journal of the American Chemical Society
|February 9, 2024
Summary
Phosphatidylglycerol (PG) activates bacterial potassium channels cooperatively, revealing concentration-dependent lipid-protein interactions crucial for ion channel regulation. This study enhances understanding of allosteric mechanisms in membrane proteins.
Area of Science:
- Biophysics
- Membrane Biology
- Structural Biology
Background:
- Lipid-protein interactions are vital for membrane protein function, including ion transport and signal transduction.
- The molecular mechanisms and functional consequences of lipid binding to membrane proteins remain incompletely understood.
- Previous research on lipid activation of ion channels primarily focused on specific signaling lipids like phosphatidylinositol bisphosphate.
Purpose of the Study:
- To elucidate the molecular details of lipid-protein interactions and their functional impact on ion channels.
- To investigate the cooperative binding and activation of a bacterial potassium channel by phosphatidylglycerol (PG).
- To explore the role of common membrane lipids in regulating ion channel activity.
Main Methods:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy to quantify PG binding to the KirBac1.1 channel.
- Coarse-grained molecular dynamics (CGMD) simulations to model lipid-protein interactions.
- Liposomal flux assays to measure potassium (K+) transport activity.
Main Results:
- Phosphatidylglycerol (PG) binds to the KirBac1.1 channel with positive cooperativity (n=3.8) and a dissociation constant (Kd) of ~7 mol% PG.
- Potassium (K+) flux through the channel increases cooperatively with PG concentration (EC50 ~20 mol%), demonstrating PG as a partial agonist with fivefold amplification.
- NMR and CGMD data confirm direct PG interaction with key channel residues, some inaccessible in the closed state.
Conclusions:
- Common membrane lipids like PG can allosterically regulate ion channel activity through concentration-dependent interactions.
- The findings highlight the significance of protein allostery and lipid-protein binding dynamics in ion channel function.
- This study provides insights relevant to the activation mechanisms of human ion channels, emphasizing the role of ubiquitous lipids.
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