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Transmembrane movements of lipids
1Institut de Biologie Physico-Chimique, Paris, France.
Experientia
|June 15, 1990
Summary
Biological membranes maintain lipid asymmetry using proteins. Phospholipid flippases and aminophospholipid translocases rapidly move specific phospholipids, establishing and maintaining membrane lipid organization in various cell types.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Biophysics
Background:
- Cell membranes exhibit lipid asymmetry, crucial for cellular functions.
- Phospholipids diffuse slowly across lipid bilayers spontaneously.
- Membrane proteins can modulate this slow diffusion.
Purpose of the Study:
- To investigate the role of proteins in phospholipid translocation across membranes.
- To identify specific phospholipid translocators in different cellular compartments.
Main Methods:
- Analysis of lipid diffusion rates in pure lipid bilayers.
- Identification and characterization of phospholipid flippases in microsomes and bacterial membranes.
- Investigation of aminophospholipid translocase activity in eukaryotic plasma membranes and chromaffin granules.
Main Results:
- Intrinsic proteins selectively modulate slow phospholipid diffusion in biological membranes.
- Non-specific phospholipid flippases facilitate rapid phospholipid redistribution in microsomes and bacterial membranes.
- Aminophospholipid translocase in eukaryotic plasma membranes selectively pumps phosphatidylserine and phosphatidylethanolamine, establishing permanent lipid asymmetry.
- The presence of aminophospholipid translocase in chromaffin granules indicates lipid translocators in eukaryotic organelles.
Conclusions:
- Proteins play a critical role in regulating phospholipid movement and membrane asymmetry.
- Specific translocases, like aminophospholipid translocase, are responsible for maintaining distinct lipid compositions in different membrane leaflets.
- Eukaryotic organelles possess lipid translocators, contributing to their specific membrane properties.