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Phosphatidylcholine mobility in liver microsomal membranes
Biochimica Et Biophysica Acta
|July 4, 1978
Summary
Rat liver microsomes readily exchange phosphatidylcholine (PC) at physiological temperatures, indicating its accessibility. However, PC within vesicles and after phospholipase A2 treatment shows altered exchange kinetics and composition, suggesting specific localization and movement within the membrane.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Dynamics
Background:
- Phosphatidylcholine (PC) is a major phospholipid in liver microsomes.
- Understanding PC localization and movement is crucial for membrane function.
Purpose of the Study:
- To investigate the accessibility and exchange dynamics of rat liver microsomal phosphatidylcholine.
- To explore the impact of temperature and phospholipase A2 treatment on PC exchange.
Main Methods:
- Utilized purified phosphatidylcholine exchange protein from bovine liver.
- Employed egg phosphatidylcholine for exchange experiments.
- Used phospholipase A2 from Naja naja for hydrolysis.
- Assessed membrane permeability changes using mannose 6-phosphate and neodymium (III) cations.
Main Results:
- Rat liver microsomal PC was fully exchangeable at 25 and 37°C, but only 60% exchangeable in lipid vesicles.
- Complex exchange kinetics were observed at lower temperatures (0 and 8°C).
- Phospholipase A2 treatment reduced PC content and altered the fatty acid profile (lower arachidonic acid).
- Exchange of remaining PC after phospholipase treatment was slower than with intact microsomes.
Conclusions:
- Rat liver microsomal phosphatidylcholine exhibits temperature-dependent accessibility for exchange.
- A portion of microsomal PC may be less accessible or differently localized within the membrane.
- Phospholipase A2 treatment affects PC composition and exchange properties, providing insights into membrane structure.