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Related Concept Videos

Ion Channels01:19

Ion Channels

The movement of ions like sodium, potassium, and calcium into and out of the cell is essential to maintain the electrochemical gradient in living cells. The ion channels—a class of membrane transport proteins—help maintain this ionic gradient for the smooth functioning of physiological activities such as maintaining cell size and volume, conducting nerve impulses, and gas and nutrient exchange.
Ion channels are specialized integral membrane proteins on the plasma membrane that allow specific...
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...
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.
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...
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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Related Experiment Video

Updated: May 13, 2026

Expression and Purification of the Human Lipid-sensitive Cation Channel TRPC3 for Structural Determination by Single-particle Cryo-electron Microscopy
08:27

Expression and Purification of the Human Lipid-sensitive Cation Channel TRPC3 for Structural Determination by Single-particle Cryo-electron Microscopy

Published on: January 7, 2019

Assembling an ion channel: ORF 3a from SARS-CoV.

Tze-Hsiang Chien1, Ya-Ling Chiang, Chin-Pei Chen

  • 1Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei, 112, Taiwan.

Biopolymers
|March 14, 2013
PubMed
Summary

Severe acute respiratory syndrome coronavirus (SARS-CoV) protein 3a

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Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
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Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells

Published on: October 1, 2010

Related Experiment Videos

Last Updated: May 13, 2026

Expression and Purification of the Human Lipid-sensitive Cation Channel TRPC3 for Structural Determination by Single-particle Cryo-electron Microscopy
08:27

Expression and Purification of the Human Lipid-sensitive Cation Channel TRPC3 for Structural Determination by Single-particle Cryo-electron Microscopy

Published on: January 7, 2019

Expression and Purification of Mammalian Bestrophin Ion Channels
08:12

Expression and Purification of Mammalian Bestrophin Ion Channels

Published on: August 2, 2018

Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
15:28

Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells

Published on: October 1, 2010

Area of Science:

  • Virology
  • Structural Biology
  • Membrane Biophysics

Background:

  • Severe acute respiratory syndrome coronavirus (SARS-CoV) encodes a 274 amino acid polytopic channel protein, designated protein 3a.
  • Protein 3a possesses three putative transmembrane domains (TMDs).

Purpose of the Study:

  • To investigate the channel activity of SARS-CoV protein 3a and its individual transmembrane domains (TMDs).
  • To characterize the ion selectivity and rectification properties of the full-length protein 3a channel.

Main Methods:

  • Synthetic peptides corresponding to TMD1, TMD2, and TMD3 were reconstituted into artificial lipid bilayers.
  • Full-length protein 3a was expressed and reconstituted into artificial lipid bilayers.
  • Channel activity, ion selectivity (PK ≈ 2 PCl), and rectification were measured.
  • The effect of calcium ions on channel activity was assessed.

Main Results:

  • Only synthetic peptides corresponding to TMD2 and TMD3 exhibited channel activity when reconstituted individually.
  • Mixtures of TMD1+TMD3 and TMD2+TMD3 peptides (1:1 ratio) induced membrane activity.
  • A 1:1:1 mixture of all three TMD peptides nearly restored channel-like behavior.
  • Full-length protein 3a reconstituted into lipid bilayers formed a weakly cation-selective, rectifying channel.
  • Nonphysiological concentrations of Ca-ions induced channel activity in the reconstituted protein 3a.

Conclusions:

  • Transmembrane domains 2 and 3 of SARS-CoV protein 3a are crucial for its channel activity.
  • The full-length protein 3a functions as a cation-selective, rectifying channel.
  • Calcium ions modulate the activity of the SARS-CoV protein 3a channel.