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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.
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The Significance of Membrane Transport01:44

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The transport of solutes across the cell membrane is essential for metabolic processes, like maintaining cell size and volume, generating the action potential, exchanging nutrients and gases, etc. Membrane transport can be either passive or active. It can be simple diffusion, facilitated, or mediated transport aided by transport proteins such as transporters and channels.
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Articles linked to this work by shared authors, journal, and citation graph.

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Trivalent anions as probes of the CFTR channel pore.

General physiology and biophysics·2024
Same author

Correction: Role of Hydrophobic Amino-Acid Side-Chains in the Narrow Selectivity Filter of the CFTR Chloride Channel Pore in Conductance and Selectivity.

The Journal of membrane biology·2024
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Role of Hydrophobic Amino-Acid Side-Chains in the Narrow Selectivity Filter of the CFTR Chloride Channel Pore in Conductance and Selectivity.

The Journal of membrane biology·2023
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Two positively charged amino acid side-chains in the inner vestibule of the CFTR channel pore play analogous roles in controlling anion binding and anion conductance.

Cellular and molecular life sciences : CMLS·2021
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Electrostatic Tuning of Anion Attraction from the Cytoplasm to the Pore of the CFTR Chloride Channel.

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Related Experiment Video

Updated: Nov 4, 2025

Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein
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Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein

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Monovalent: Divalent Anion Selectivity in the CFTR Channel Pore.

Paul Linsdell1

  • 1Department of Physiology & Biophysics, Dalhousie University, Halifax, NS, Canada. paul.linsdell@dal.ca.

Cell Biochemistry and Biophysics
|May 25, 2021
PubMed
Summary

Cystic fibrosis transmembrane conductance regulator (CFTR) channels poorly bind and permeate divalent anions like thiosulfate and sulfate. Pore mutations enhancing positive charge increase divalent anion block, indicating CFTR favors monovalent chloride ions.

Keywords:
Anion selectivityChloride channelCystic fibrosis transmembrane conductance regulatorDivalent anionsIon bindingIon permeation

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Area of Science:

  • Ion channel biophysics
  • Molecular physiology
  • Membrane transport

Background:

  • Cystic fibrosis transmembrane conductance regulator (CFTR) is a crucial chloride channel.
  • CFTR exhibits weak selectivity among small monovalent anions.
  • CFTR's discrimination between monovalent and divalent anions remains poorly understood.

Purpose of the Study:

  • To investigate the interaction of divalent anions (thiosulfate, sulfate) with CFTR.
  • To determine CFTR's ability to discriminate between monovalent and divalent anions.
  • To analyze the role of pore charge in divalent anion interaction with CFTR.

Main Methods:

  • Patch clamp electrophysiology on wild-type and mutant human CFTR channels.
  • Assessment of anion block and permeability using specific divalent anions.
  • Voltage-dependent analysis of anion binding affinities.

Main Results:

  • Wild-type CFTR showed weak block by intracellular thiosulfate (<20%) and sulfate (<5%) at 10 mM.
  • Mutations (I344K, S1141K) introducing positive charge in the pore significantly enhanced intracellular divalent anion block.
  • Divalent anion permeability through wild-type and mutant CFTR was immeasurably low, less than 1% of chloride permeability.

Conclusions:

  • CFTR demonstrates strong selectivity for monovalent over divalent anions in both binding and permeability.
  • The pore's positive charge density is optimized to disfavor divalent anion binding.
  • This selectivity is a key aspect of CFTR's physiological function in chloride transport.