Related Experiment Videos
Multi-ion pore behaviour in the CFTR chloride channel
J A Tabcharani1, J M Rommens, Y X Hou
1Department of Physiology, McGill University, Montréal, Québec, Canada.
Nature
|November 4, 1993
Summary
Cystic fibrosis transmembrane conductance regulator (CFTR) channels can conduct multiple anions at once. Altering specific residues impacts this multi-ion pore behavior, potentially explaining cystic fibrosis disease mechanisms.
Area of Science:
- Ion channel biophysics
- Molecular mechanisms of epithelial transport
Background:
- Cystic fibrosis transmembrane conductance regulator (CFTR) is crucial for chloride transport in epithelia.
- CFTR dysfunction causes cystic fibrosis (CF).
- The physical basis of CFTR permeation and the role of specific residues remain unclear.
Purpose of the Study:
- To investigate multi-ion permeation in CFTR.
- To elucidate the physical basis of altered halide selectivity and conductance due to CFTR mutations.
- To explore the role of residue Arg 347 in CFTR ion conduction.
Main Methods:
- Whole-cell electrophysiology to study CFTR conductance.
- Single-channel recordings to analyze ion permeation.
- Site-directed mutagenesis to investigate residue function (Arg 347).
- pH manipulation to assess channel behavior.
Main Results:
- Wild-type CFTR exhibits multi-ion occupancy.
- An anomalous mole fraction effect was observed with mixed permeant anions, indicating simultaneous ion passage.
- Replacing Arg 347 with aspartate abolished this effect.
- Replacing Arg 347 with histidine allowed pH-dependent toggling of the effect.
- Mutations at Arg 347 alter CFTR single-channel conductance and halide selectivity.
Conclusions:
- CFTR channels can accommodate multiple anions simultaneously.
- The residue at position 347 critically influences multi-ion pore behavior.
- Loss of multiple anion occupancy due to mutations may underlie CF pathogenesis.
- CFTR serves as a model for studying multi-ion channel conduction.