Related Experiment Video
Updated: May 24, 2026
10:19
Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
Published on: January 10, 2011
Selectivity filter gating in large-conductance Ca(2+)-activated K+ channels
Jill Thompson1, Ted Begenisich
1Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
The Journal of General Physiology
|February 29, 2012
Summary
Large-conductance, calcium-activated potassium (BK) channels are not gated by a cytoplasmic gate. Instead, ion interactions reveal that BK channels are likely gated by the pore selectivity filter, unlike other voltage-gated potassium channels.
Area of Science:
- Molecular Biology
- Ion Channel Physiology
- Biophysics
Background:
- Voltage-gated potassium (K(v)) channels control ion passage via a physical gate, typically located at the cytoplasmic end of the pore.
- The gating mechanism of large-conductance, voltage- and Ca(2+)-activated potassium (BK) channels remains debated, with some evidence suggesting a cytoplasmic gate and other evidence pointing to the pore selectivity filter.
Purpose of the Study:
- To investigate the gating mechanism of BK channels by examining the interaction of blockers with channel gating.
- To determine if BK channels possess a cytoplasmic gate or are gated by the pore selectivity filter.
Main Methods:
- Tested the effects of tetrabutyl ammonium (TBA) and the Shaker 'ball' peptide (BP) on BK channels using either potassium (K+) or rubidium (Rb+) as the permeant ion.
- Compared the behavior of BK channels with cytoplasmically gated Shaker K channels under the same conditions.
- Analyzed blocker interactions and interference with channel closing based on the permeant ion.
Main Results:
- In K+ solutions, TBA and BP acted as open-channel blockers for BK channels, with BP interfering with channel closing.
- When Rb+ replaced K+, TBA and BP blocked both closed and open BK channels, and BP no longer affected channel closing.
- Interactions of TBA and BP with Shaker K channels were independent of the permeant ion, showing opposite behavior to BK channels.
Conclusions:
- The permeant ion-dependent behavior of blockers on BK channels strongly argues against a cytoplasmic gate.
- Results provide significant evidence supporting selectivity filter gating in BK channels.
- This study offers a positive test for selectivity filter gating as the mechanism for BK channel regulation.
Related Concept Videos
01:19The Role of Ion Channels in Neuronal Computation
A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
01:26Voltage-gated Ion Channels
Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
01:26Voltage-gated Ion Channels
Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
01:30Ligand-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...
01:24Non-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.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
01:24Non-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.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.