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Mapping apolipoprotein B on the low density lipoprotein surface by immunoelectron microscopy.
J E Chatterton1, M L Phillips, L K Curtiss
1Department of Chemistry and Biochemistry, University of California, Los Angeles 90024-1569.
The Journal of Biological Chemistry
|March 25, 1991
Summary
This study maps Apolipoprotein B (apoB) on low-density lipoprotein (LDL) using electron microscopy. Results show apoB spans at least half the LDL surface, indicating restricted flexibility and providing insights into lipoprotein structure.
Area of Science:
- Biochemistry
- Structural Biology
- Lipid Metabolism
Background:
- Apolipoprotein B (apoB) is the primary protein component of low-density lipoprotein (LDL).
- Understanding apoB's structure on the LDL surface is crucial for lipoprotein metabolism and cardiovascular disease research.
Purpose of the Study:
- To map the spatial distribution of Apolipoprotein B (apoB) epitopes on the surface of low-density lipoprotein (LDL).
- To determine the extent and flexibility of apoB on the LDL particle.
Main Methods:
- Utilized electron microscopy to visualize monoclonal antibody binding sites on LDL.
- Correlated antibody binding sites with established apoB polypeptide sequence locations.
- Calculated angular distances between epitope pairs to determine relative placement on the LDL sphere.
Main Results:
- Successfully mapped six epitopes of apoB on the LDL surface.
- Demonstrated that apoB extends over at least a hemisphere of the LDL particle.
- Observed restricted flexibility of apoB, evidenced by standard deviations in epitope latitude and longitude.
Conclusions:
- Apolipoprotein B (apoB) occupies a significant portion of the low-density lipoprotein (LDL) surface.
- The spatial arrangement suggests limited conformational flexibility of apoB.
- Further epitope mapping may clarify if apoB completely encircles the LDL particle.