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Related Concept Videos

Ligand-Gated Ion Channel Receptor: Gating Mechanism01:30

Ligand-Gated Ion Channel Receptor: Gating Mechanism

Ligand-gated ion channels are transmembrane proteins that play a vital role in intercellular communication and functions of the nervous system. They allow the influx of ions across the membrane once the neurotransmitter binds, allowing the subsequent transmission of electrical excitation across the neurons. Other ligand-gated ion channels, like the γ-aminobutyric acid (GABA) receptor, permit anions like chloride into the cells on the binding of the GABA molecule. Their entry into the cell...
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Ligand-gated Ion Channels01:19

Ligand-gated Ion Channels

Ligand-gated ion channels are transmembrane proteins with a channel for ions to pass through and a binding site for a ligand. The channel opens only when a ligand attaches to the binding site.
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that include the...
Ligand-gated Ion Channels01:19

Ligand-gated Ion Channels

Ligand-gated ion channels are transmembrane proteins with a channel for ions to pass through and a binding site for a ligand. The channel opens only when a ligand attaches to the binding site.
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Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that include the...
Non-gated Ion Channels01:24

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
Non-gated Ion Channels01:24

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.

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Updated: Jul 2, 2026

Inhibitory Synapse Formation in a Co-culture Model Incorporating GABAergic Medium Spiny Neurons and HEK293 Cells Stably Expressing GABAA Receptors
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A conserved salt bridge critical for GABA(A) receptor function and loop C dynamics.

Srinivasan P Venkatachalan1, Cynthia Czajkowski

  • 1Department of Physiology, University of Wisconsin-Madison, 601 Science Drive, Madison, WI 53711, USA.

Proceedings of the National Academy of Sciences of the United States of America
|September 2, 2008
PubMed
Summary

A key salt bridge in GABA(A) receptors regulates channel opening. Agonist binding restricts loop C movement, controlling ion channel gating for brain signaling.

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Using an α-Bungarotoxin Binding Site Tag to Study GABA A Receptor Membrane Localization and Trafficking

Published on: March 28, 2014

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Biochemistry

Background:

  • Ligand-gated ion channels (LGICs) mediate rapid chemical signaling in the brain.
  • LGICs are allosteric proteins that transition between closed, open, and desensitized states upon ligand binding.
  • Understanding the protein dynamics of LGIC conformational changes is crucial, particularly the role of loop C movements in channel gating.

Purpose of the Study:

  • To identify key residues and interactions regulating loop C position in GABA(A) receptors.
  • To investigate the role of a specific intrasubunit salt bridge in GABA(A) receptor activation and gating.
  • To probe the mobility of loop C during resting and ligand-bound states.

Main Methods:

  • Site-directed mutagenesis to create charge reversal and alanine substitution mutants (betaE153, betaK196).
  • Functional assays measuring EC(50) for GABA, pentobarbital, and propofol.
  • Mutant cycle analysis to assess energetic coupling between residues.
  • Disulfide bond formation assays using cysteine substitutions (E153C-K196C) to monitor loop C mobility.

Main Results:

  • Charge reversal mutations (E153K, K196E) in the GABA(A) receptor altered EC(50) values, indicating critical roles in activation.
  • A charge swap mutation (E153K-K196E) partially rescued receptor function, suggesting a functional electrostatic interaction.
  • Mutant cycle analysis confirmed energetic coupling between E153 and K196.
  • Disulfide bond formation was reduced upon addition of GABA or pentobarbital, indicating restricted loop C mobility upon activation.

Conclusions:

  • A conserved intrasubunit salt bridge involving betaE153 and betaK196 is critical for GABA(A) receptor activation.
  • Agonist binding to the GABA(A) receptor restricts the mobility of the loop C region.
  • This restriction of loop C movement is a key step in the allosteric gating mechanism of the GABA(A) receptor.