Related Experiment Video
Updated: Aug 14, 2026
07:47
A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters
Published on: April 20, 2015
Ion-binding properties of the ClC chloride selectivity filter
Séverine Lobet1, Raimund Dutzler
1Department of Biochemistry, University of Zürich, Zürich, Switzerland.
The EMBO Journal
|December 13, 2005
Summary
The ClC channel selectivity filter has three ion-binding sites that bind chloride ions. These properties are conserved in bacterial and human proteins, linking ion permeation and transport.
Area of Science:
- Molecular Biology
- Structural Biology
- Biophysics
Background:
- Chloride (Cl-) channels and transporters are vital protein families with conserved transmembrane architecture.
- Understanding their ion-binding mechanisms is crucial for elucidating cellular transport processes.
Purpose of the Study:
- To investigate the ion-binding properties of the ClC selectivity filter using a bacterial homolog, EcClC.
- To compare these properties with human ClC-1 channels, exploring functional conservation.
Main Methods:
- Crystallographic study of the Escherichia coli ClC (EcClC) homolog.
- Analysis of ion-binding sites within the selectivity filter.
Main Results:
- The ClC selectivity filter contains three distinct ion-binding sites.
- These sites bind chloride ions with millimolar affinity and can be simultaneously occupied.
- Ion-binding properties are conserved between EcClC and human ClC-1.
Conclusions:
- A conserved functional link exists between ion permeation in ClC channels and active transport in ClC transporters.
- Chloride ions permeate ClC channels in single file, with mutual repulsion facilitating rapid conduction, similar to K+ channels.
Related Concept Videos
01:03Affinity Chromatography
Affinity chromatography is a powerful technique extensively utilized for separating and purifying specific biomolecules from complex mixtures. It capitalizes on the highly selective binding between an analyte and its counterpart, such as antibody-antigen interactions. The counterpart is immobilized on the stationary phase, forming an affinity column. The stationary phase typically consists of solid support, such as agarose or porous glass beads, immobilizing the affinity ligand. The mobile...
01:09Ion-Exchange Chromatography
Ion-exchange chromatography, or IEC, is a technique for separating ions based on their affinity for the stationary phase. The stationary phase is a cross-linked polymer resin with covalently attached ionic functional groups. The functional groups can be either positively charged (cation exchangers) or negatively charged (anion exchangers). A cation exchanger consists of a polymeric anion and active cations, while an anion exchanger is a polymeric cation with active anions. The choice of...
01:31Transport Number
The transport number is the fraction of the total current carried by an ion in an electrolyte solution. It is defined as the ratio of the current carried by a specific ion to the total current flowing through the solution. The transport number, t, is central to understanding ionic mobility, which describes how fast an ion moves under the influence of an electric field. This link connects the physical behavior of ions in solution to the chemical processes that occur during electrochemical...
01:17Ion Exchange
Ion exchange chromatography separates charged molecules from a solution by reversibly exchanging them with mobile, or 'active', ions associated with the oppositely charged stationary phase. This method can be used to separate ions, soften and deionize water, and purify solutions. The polymers comprising the ion-exchange column are high-molecular-weight and chemically stable polymers, crosslinked to be porous and essentially insoluble. They are also functionalized with either acidic or basic...
02:40Ligand Binding Sites
Proteins are dynamic macromolecules that carry out a wide variety of essential processes; however, the activities of most proteins depend on their interactions with other molecules or ions, known as ligands.
Protein-ligand interactions are quite specific; even though numerous potential ligands surround a cellular protein at any given time, only a particular ligand can bind to that protein. Moreover, a ligand binds only to a dedicated area on the surface of the protein, known as the...
Protein-ligand interactions are quite specific; even though numerous potential ligands surround a cellular protein at any given time, only a particular ligand can bind to that protein. Moreover, a ligand binds only to a dedicated area on the surface of the protein, known as the...
00:56Extraction: Advanced Methods
Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is formed in...