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Related Concept Videos

Ion Channels01:19

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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...
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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.
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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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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.
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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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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.
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Recapitulation of an Ion Channel IV Curve Using Frequency Components
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Selectivity filter ion binding affinity determines inactivation in a potassium channel.

Céline Boiteux1, David J Posson2,3, Toby W Allen4

  • 1School of Science, RMIT University, Melbourne, VIC 3001, Australia.

Proceedings of the National Academy of Sciences of the United States of America
|November 6, 2020
PubMed
Summary

The MthK potassium channel

Keywords:
crystallographyinactivationmolecular dynamicspotassium channelselectivity filter

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Area of Science:

  • Structural Biology
  • Biophysics
  • Ion Channel Physiology

Background:

  • Potassium channels regulate ion transport, crucial for cellular function.
  • Inactivation, often via the selectivity filter (SF), controls channel conductivity.
  • The role of the SF in ligand-gated channels like MthK is not fully understood.

Purpose of the Study:

  • To investigate the conformational changes and ion binding dynamics of the MthK channel's selectivity filter.
  • To compare the MthK SF's behavior with other potassium channels like KcsA.

Main Methods:

  • X-ray crystallography to determine MthK structures at various potassium concentrations.
  • Molecular simulations to model SF behavior and ion interactions.
  • Analysis of ion binding affinities and site-specific occupancy.

Main Results:

  • MthK structures remained conductive across a wide range of K+ concentrations (6-150 mM).
  • Three SF sites showed high K+ affinity, while one site (S2) exhibited low affinity (~50 mM).
  • MthK SF collapse occurs without K+, but single ion binding can restore conductivity, unlike KcsA.

Conclusions:

  • MthK's SF exhibits unique ion titration properties due to differential binding site affinities.
  • Specific interactions within the MthK SF, particularly at the S2 site, influence its conductivity.
  • These findings explain the distinct inactivating phenotypes between MthK and KcsA channels.