Evidence for the identity of the major apoprotein in low density and very low density lipoproteins in normal subjects and patients with familial hyperlipoproteinemia

Abstract

A B S T R A C T The major apoprotein (s) from human plasma low density lipoproteins was isolated and compared with a major protein fraction (fraction I) from very low density lipoproteins (VLDL). Fraction I had been previously found to comprise approximately 40% of the total protein of VLDL. Fraction I from VLDL and apoLDL from normal subjects were indistinguishable in amino acid compositions and circular dichroic spectra. They yielded indistinguishable displacement curves of LDL-'I by radioimmunoassay and formed immunoprecipitin lines of complete identity. Fraction I from VLDL of normal subjects was compared with the fraction isolated from patients with familial types II, III, IV, and V hyperlipoproteinemia. There were no detectable differences between any of these fractions in amino acid compositions, circular dichroic spectra, and immunochemical properties. It was, therefore, concluded that short of peptide mapping or determination of amino acid sequences, fraction I from VLDL of each subject with familial hyperlipoproteinemia appears to be identical with fraction I and apoLDL from normal individuals.A new convenient method of preparation of soluble apoLDL, modified from a procedure previously described from this laboratory, is presented.

Identification of apolipoproteins in lipoprotein density classes of hypercholesterolemia (type IIa)

“…Our study confirmed the report of Gotto et al [24], that ApoB in type IIa hyperlipoproteinemia is immunochemically identical to ApoB from normal plasma. In addition, all the identified apolipoproteins and their polypeptides in type Ila hyperlipoproteinemia are immunochemically and electrophoretically identical to those from normal plasma.…”

Quantification of apolipoprotein B in grossly normal human aorta.

“…Lipid-free LDL and VLDL were prepared by delipidation at 4 C C with diethyl ether-ethanol (3:1). 20 The apoB was purified by fractionation of lipid-free LDL on Sephadex G-150 as described previously. 20 Antisera against apoB were raised in goats and were partially purified by affinity chromatography using LDL-Sepharose.…”

“…20 The apoB was purified by fractionation of lipid-free LDL on Sephadex G-150 as described previously. 20 Antisera against apoB were raised in goats and were partially purified by affinity chromatography using LDL-Sepharose. 17 The antisera gave precipitin lines of complete identity against LDL and VLDL but did not react with human serum albumin, high density lipoproteins (HDL) and its major apoproteins, apoA-I or apoA-II, or the apoC proteins, 21 either on double gel diffusion plates or in the electroimmunodiffusion (EID) system described below.…”

“…20 The apoproteins were then chromatographed on Sephadex G-150, 20 and the concentration of the apoB present in the void volume of the column was determined by amino acid analyses.…”

Apoprotein B in fasting and postprandial human jejunal mucosa.

“…Many of these apoproteins have been isolated and characterized from human plasma and most of them are present in more than one lipoprotein family. Apoprotein B constitutes more than 95% of the protein moiety of low density lipoproteins (LDL) (8), and also represents 22 and 30-40% of the protein moieties of chylomicrons and VLDL, respectively (9,10). The apoprotein B appears to be required for the transport of lipoprotein particles out of the absorptive cell and into the lymph.…”