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Pulmonary surfactant proteins insert cation-permeable channels in planar bilayers.
1Center for Pediatric Research, Department of Pediatrics, Children's Hospital of The King's Daughters and Eastern Virginia Medical School, 855 West Brambleton Avenue, Norfolk, Virginia 23510, USA. doelberg@chkd.com
Molecular Genetics and Metabolism
|September 20, 2000
Summary
Hydrophobic proteins in pulmonary surfactant form ion channels in membranes, contributing to lung function beyond surface tension reduction. This discovery reveals a novel mechanism for surfactant
Area of Science:
- Biophysics
- Pulmonary Physiology
- Membrane Biology
Background:
- Pulmonary surfactant reduces surface tension for lung ventilation.
- Surfactants with hydrophobic proteins have unexplained biological effects.
- Hypothesis: Hydrophobic proteins form membrane channels.
Purpose of the Study:
- To investigate if hydrophobic surfactant proteins insert into membranes and form channels.
- To elucidate the mechanism behind the biological effects of pulmonary surfactant.
Main Methods:
- Electrophysiological monitoring of planar lipid bilayers.
- In vitro model using intact surfactant and extracted surfactant proteins.
- Reconstitution of proteins with phospholipids or direct addition to lipids.
Main Results:
- Both intact surfactant and extracted proteins induced gated channel activities.
- Channels exhibited slope conductances of approximately 40 pS.
- Monovalent cation conductance was confirmed, with selectivity for smaller cations.
Conclusions:
- Hydrophobic surfactant proteins induce channel-mediated transport in artificial membranes.
- Surfactant proteins may contribute to lung physiology and therapeutics via cation channel insertion.
- This mechanism offers a new perspective on surfactant function in the lungs.