Characterization of lipoproteins containing a truncated form of apolipoprotein B, apolipoprotein B32.
We have characterized the lipoproteins isolated from the plasma of a human subject who was heterozygous for a mutation yielding a truncated apolipoprotein B (apo-B32). The apo-B32 lipoproteins were isolated from the plasma high density lipoprotein (HDL) fraction by heparin-Sepharose chromatography. Although the chemical composition of the apo-B32-containing lipoproteins was similar to that of normal HDL, the mean diameter of the apo-B32 lipoproteins was larger than typical apo-AI-containing HDL particles. On agarose gels, the apo-B32 lipoproteins had pre-beta mobility similar to that of normal very low density lipoproteins. Analysis of the purified apo-B32 lipoproteins by SDS-polyacrylamide gel electrophoresis revealed the presence of both apo-AI and apo-E. In order to further analyze the properties of apo-B32, we developed an apo-B32 expression vector and generated stable rat hepatoma cell lines expressing apo-B32. In these cell lines, the apo-B32 protein was secreted in a d > 1.21 g/ml lipoprotein. Oleic acid supplementation of the cell-culture media had no measurable affect on the density distribution of the apo-B32 lipoproteins that were secreted by the cells.
McCormick
S P
SP
Pathology Department, Christchurch School of Medicine, Christchurch Hospital, New Zealand.
Day
W A
WA
George
P M
PM
D000818:Animals; D016632:Apolipoprotein A-I / Q000032:analysis; D001055:Apolipoproteins B / Q000097:blood / Q000737:chemistry* / Q000235:genetics; D001057:Apolipoproteins E / Q000032:analysis; D015153:Blotting, Western; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D015870:Gene Expression; D006579:Heterozygote; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood*; D008077:Lipoproteins, LDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008854:Microscopy, Electron; D009154:Mutation; D010316:Particle Size; D014162:Transfection
D016632:Apolipoprotein A-I; D001055:Apolipoproteins B; D001057:Apolipoproteins E; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL