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Electrophoretic mobility of microsomes from rat liver
Journal of Cell Science
|February 1, 1977
Summary
Investigating microsome surface charge reveals that ribosome removal reduces mobility. Proteolytic and phospholipase treatments alter smooth microsome electrophoretic mobility, indicating underlying protein structures influence surface charge.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Biophysics
Background:
- Microsomes are essential cellular components involved in protein synthesis and lipid metabolism.
- Understanding the surface charge and composition of microsomes is crucial for elucidating their function and interactions.
- Differences in electrophoretic mobility between rough and smooth microsomes suggest variations in their surface properties.
Purpose of the Study:
- To investigate the electrophoretic mobilities of rough and smooth microsomes.
- To determine the contribution of ribosomes and surface proteins/lipids to microsomal surface charge.
- To explore the structural differences between normal and induced smooth liver microsomes.
Main Methods:
- Free electrophoresis in a sucrose gradient was employed to analyze microsomal electrophoretic mobilities.
- Enzymatic treatments, including neuraminidase, phospholipases (C, D, A), trypsin, and papain, were used to probe surface components.
- Comparative analysis of mobility changes in response to various treatments was performed.
Main Results:
- Rough microsomes exhibit higher net negative surface charge compared to smooth microsomes; ribosome removal equalizes their mobility.
- Trypsin, papain, and phospholipase A treatments significantly alter smooth microsome electrophoretic mobility, suggesting the presence of accessible charged proteins and lipids.
- Re-treatment of trypsin-digested microsomes with phospholipase C restores original mobility, indicating buried negatively charged proteins, not lipid phosphates, are responsible for the effect.
- Induced smooth liver microsomes show altered protein composition but unchanged electrophoretic mobility upon trypsin treatment, suggesting structural differences.
Conclusions:
- Microsomal surface charge is significantly influenced by both ribosomes and surface-associated proteins.
- Specific protein components, rather than lipid phosphates, are major determinants of smooth microsome electrophoretic mobility.
- Phenobarbital-induced changes in liver microsomes result in distinct membrane structures compared to control membranes.