Human very low density lipoprotein structure: interaction of the C apolipoproteins with apolipoprotein B-100.

Very low density lipoproteins (VLDL) are a heterogenous population of particles differing in size and composition. Heparin-Sepharose chromatography yields three VLDL subfractions. Two subfractions, VLDLNR-1 and VLDLNR-2, which are not retained by heparin, contain little or no detectable apolipoprotein (apo)E. According to negative stain electron microscopy, VLDLNR-1 is slightly larger than VLDLNR-2. The third fraction, VLDLR, is composed of smaller particles that are retained by the heparin-Sepharose and contain apoE. The C apolipoproteins of the respective VLDL subfractions transfer to 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) single bilayer vesicles giving three subfractions designated VLDLNR-1-C, VLDLNR-2-C, and VLDLR-C. The protein, phospholipid, and cholesterol (free + esterified) contents decrease in the order VLDLR > VLDLNR-2 > VLDLNR-1. Triglyceride content decreases in the opposite order. POPC treatment of each VLDL subfraction increases the phospholipid and decreases the protein, triglyceride, and cholesteryl ester contents, while free cholesterol remains unchanged. According to immunological analysis of each subfraction with well-characterized monoclonal antibodies, the accessibility of some epitopes of apoB-100 on VLDL is changed by POPC treatment. Electron-microscopic analysis of POPC-treated VLDL subfraction reveals vacancies on the surfaces of each particle. VLDLNR-1, VLDLNR-2, and VLDLR are resistant to thrombin cleavage, whereas the lipoproteins lacking C apolipoproteins are not. Thrombin cleavage (8 h) of apoB-100 of VLDLNR-2-C and VLDLR-C gives two fragments, T1 and T2, that are converted to smaller fragments only after prolonged treatment. In contrast, apoB-100 of VLDLNR-1-C is converted into small fragments after 8 h thrombin treatment. These results suggest that removal of apoCs affects the accessibility and conformation of apoB-100 in the individual VLDL subfractions in the region near residue 3249, which is the primary thrombin cleavage site and the epitope of monoclonal antibody 4C11.

[1]  J. Breslow,et al.  Hypertriglyceridemia as a result of human apo CIII gene expression in transgenic mice. , 1990, Science.

[2]  Y. Marcel,et al.  Use of bacterial expression cloning to localize the epitopes for a series of monoclonal antibodies against apolipoprotein B100. , 1990, The Journal of biological chemistry.

[3]  C. Fielding,et al.  Apolipoprotein E mediates binding of normal very low density lipoprotein to heparin but is not required for high affinity receptor binding. , 1989, The Journal of biological chemistry.

[4]  Y. Marcel,et al.  Rat monoclonal antibodies to human apolipoprotein B: advantages and applications. , 1989, Journal of lipid research.

[5]  J. B. Massey,et al.  Apolipoproteins C-I, C-II, and C-III: kinetics of association with model membranes and intermembrane transfer. , 1988, Biochemistry.

[6]  C. Fielding,et al.  A change in apolipoprotein B expression is required for the binding of apolipoprotein E to very low density lipoprotein. , 1988, The Journal of biological chemistry.

[7]  J. Fruchart,et al.  A monoclonal antibody (BIP 45) detects Ag(c,g) polymorphism of human apolipoprotein B. , 1987, Journal of immunological methods.

[8]  R. Havel,et al.  Metabolism of lipoproteins containing apolipoprotein B-100 in blood plasma of rabbits: heterogeneity related to the presence of apolipoprotein E. , 1986, Proceedings of the National Academy of Sciences of the United States of America.

[9]  C. Fielding,et al.  An apo-E-free very low density lipoprotein enriched in phosphatidylethanolamine in human plasma. , 1986, The Journal of biological chemistry.

[10]  S. Young,et al.  Conservation of the Low Density Lipoprotein Receptor‐Binding Domain of Apoprotein B , 1986, Arteriosclerosis.

[11]  E. Krul,et al.  Roles of apolipoproteins B and E in the cellular binding of very low density lipoproteins. , 1985, The Journal of clinical investigation.

[12]  B. Pau,et al.  Monoclonal antibodies to low density lipoprotein used for the study of low- and very-low-density lipoproteins, in "ELISA" and immunoprecipitation technics. , 1984, Biochemical and Biophysical Research Communications - BBRC.

[13]  J. Chao,et al.  Degradation of apolipoprotein B-100 of human plasma low density lipoproteins by tissue and plasma kallikreins. , 1984, Journal of Biological Chemistry.

[14]  S. Grundy,et al.  Isopropanol precipitation method for the determination of apolipoprotein B specific activity and plasma concentrations during metabolic studies of very low density lipoprotein and low density lipoprotein apolipoprotein B. , 1983, Journal of lipid research.

[15]  A. Catapano,et al.  Subfractionation of human very low density lipoproteins by heparin-Sepharose affinity chromatography. , 1983, Journal of Lipid Research.

[16]  R. Jackson,et al.  Sulfhydryl chemistry and solubility properties of human plasma apolipoprotein B. , 1982, Biochemistry.

[17]  A. Catapano The distribution of apo C-II and apo C-III in very low density lipoproteins of normal and type IV subjects. , 1980, Atherosclerosis.

[18]  D. Ballantyne,et al.  Changing relative proportions of apolipoproteins CII and CIII of very low density lipoproteins in hypertriglyceridaemia. , 1976, Atherosclerosis.

[19]  R. Havel,et al.  Lipoproteins and lipid transport. , 1975, Advances in experimental medicine and biology.

[20]  R. Krauss,et al.  Further Observations on the Activation and Inhibition of Lipoprotein Lipase by Apolipoproteins , 1973, Circulation research.

[21]  W. Brown,et al.  Inhibition of lipoprotein lipase by an apoprotein of human very low density lipoprotein. , 1972, Biochemical and biophysical research communications.

[22]  A. Helenius,et al.  Removal of lipids from human plasma low-density lipoprotein by detergents. , 1971, Biochemistry.

[23]  J. Larosa,et al.  A specific apoprotein activator for lipoprotein lipase. , 1970, Biochemical and biophysical research communications.

[24]  U. K. Laemmli,et al.  Cleavage of structural proteins during , 1970 .

[25]  R. Havel,et al.  The distribution and chemical composition of ultracentrifugally separated lipoproteins in human serum. , 1955, The Journal of clinical investigation.

[26]  O. H. Lowry,et al.  Protein measurement with the Folin phenol reagent. , 1951, The Journal of biological chemistry.