Precipitation of iodine-125-labeled lipoproteins with specific polypeptide antisera. Evidence for two populations with differing polypeptide compositions in human high density lipoproteins

Albers, John J.; Aladjem, Frederick

doi:10.1021/bi00794a019

Cited by 122 publications

(29 citation statements)

References 13 publications

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“…The spur, indicated partial identity (38) between anti-A-I and anti-A-11, suggests the presence of two species of A-I-containing lipoproteins; one of these designated lipoprotein A (LP-A) contains both A-I and A-11, whereas the other contains only A-I and probably corresponds to LP-A-I found in the adult system. These two lipoprotein forms of A-I have been previously reported for the human adult system (6,48). The reaction of identity between antisera to C-I, C-11, and C-I11 when tested against cord serum indicates the presence of a lipoprotein species containing C-I, C-11, and C-I11 polypeptides.…”

Section: Methodssupporting

confidence: 53%

Studies on the Apolipoproteins and Lipoproteins of Cord Serum

McConathy

Lake

1980

Pediatr Res

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SummaryStudies on the cord serum lipid transport system were initiated to determine whether there is a correlation between decreased cord serum lipid levels and the absence or diminished level of some or all of the human serum apolipoproteins. Immunologic studies indicated the presence of all the well-characterized apolipoproteins and provided evidence that these apolipoproteins occurred primarily as distinct lipoprotein species with a paucity of association complexes or what others have termed "triglyceride-rich" lipoproteins. Quantitation of the apolipoproteins present in cord serum by electroimmunoassay yielded the following mean levels: A-I = 730 mg/liter; A-11 = 410 &liter; apolipoprotein B = 280 mg/ liter; C-I = 59 mg/liter; C-I1 = 32 &liter; C-111 = 65 mg/liter; apolipoprotein D = 37 &liter; and apolipoprotein E = 85 mg/ liter. Levels of C-I, C-11, and apolipoprotein E approached adult levels (83 to 86% of the adult levels), whereas apolipoproteins B and D were most reduced when compared to the adult concentrations, 29 and 37%, respectively. The three other apolipoproteins were present at approximately one-half the levels found in adults. SpeculationThe immunochemical studies on the apolipoprotein levels and lipoprotein forms of cord serum provide part of the data necessary for studying the progressive changes in the human lipid transport system from its fetal form to that of the adult.Studies on the human adult serum lipid transport system have established that the major serum lipids (triacylglycerol, cholesterol, cholesteryl esters, and phospholipids) are bound to particular protein constituents (14, 32). designated apolipoproteins. Such lipid-protein complexes (lipoproteins) have been most commonly classified on the basis of two of their characteristic physical properties. i.e., hydrated density (26) and charge (30).Studies on the antigenic components of the major lipoprotein density classes and electrophoretic bands in the human adult have clearly demonstrated their protein heterogeneity (4, 37) and lead to a classification system based on apolipoproteins as the only distinct chemical markers of this system (1, 2). This concept has been developed into the lipoprotein family theory and has been described elsewhere (2). Recently, the levels of all well-recognized apolipoproteins have been reported (3).Application of these physicochemical techniques to cord sera has established that compared to normal adult levels, very low density lipoprotein (VLDL) is virtually absent (39) or present in low concentrations (13, 15), low-density lipoprotein (LDL) is markedly decreased (8,42), and the predominant lipoprotein density class is high-density lipoprotein (49). In addition, the lipid levels of cord sera are also lower than the corresponding levels in adult sera (42,49,50). However, it has not been established whether there is a correlation between the decreased cord serum lipid levels (42,49,50) and the absence or diminished level of some or all of the apolipoproteins. The studies described herein are the first...

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Section: Methodssupporting

confidence: 53%

Studies on the Apolipoproteins and Lipoproteins of Cord Serum

McConathy

Lake

1980

Pediatr Res

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“…The peptide ratio apoAI :apoAII of the high-density subfraction isolated in fixed-angle rotors has not been investigated entirely but it was assumed that no difference exists [26]. The existence of a lipoprotein subfamily with only apoAI as polypeptide has previously been reported by several investigators [5,21,26,29], but it was not clear to which density range it belonged. Results of…”

Section: Discussionmentioning

confidence: 99%

Polypeptide Distribution of the Main Lipoprotein Density Classes Separated from Human Plasma by Rate Zonal Ultracentrifugation

et al. 1974

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The polypeptide distribution of lipoprotein density fractions isolated from normal human serum by rate zonal ultracentrifugation was investigated by polyacrylamide gel electrophoresis and qualitative and quantitative immunochemical methods. I n very-low-density lipoproteins all known apoA and apoC peptides were present in amounts similar to these preparations from fixed-angle rotors. Low-density apolipoproteins consisted primarily of apoB (98 Oi0) but some small amounts of apoAIII and apoCIII were also present. No region of 100 apoB, uncontaminated by A and C peptides could be isolated by subfractionation of the low-density peak. There were marked differences in thc protein part of the high-density lipoprotein subfractions 2 and 3, as compared to these subfractions separated in the angle-head rotor. The weight ratio apoAI : apoAII was found to be approximately three times as high for subfraction 2 as for subfraction 3. I n addition, apoAIII was detectable only in subfraction 3. Of the known apoC peptides, apoCII was present in both fractions only in trace amounts, while the concentration of apoCI was in the order of I o/o and that of apoCIII, and of apoCIII, in the order of 1.5 O i 0 . Apolipoprotein B was not detectable in subfraction 2 . Two density regions were found with small amounts of lipoproteins consisting only of apoAI polypeptides. A peak corresponding to subfraction 1 of the highdensity lipoprotein from fixed-angle rotor preparations could not be detected in the eluate of zonal rotors after 24-h runs; the low-density lipoprotein peak was symmetrical in all experiments. Lipoproteins present in the bottom fraction amounted to about 2.5-4O/, of the total lipoprotein content. The only apolipoprotein found in this fraction was apoA1.It now seems to be widely accepted that individual lipoprotein density classes are composed of several lipoprotein families, i.e. separate entities with identical prot,ein moities [l -41. Although from analytical isoelectric focusing experiments a minimum of 8 different lipoprotein subpopulations can be expected [5], only three main lipoprotein families could be isolated from human plasma on a preparative scale and characterized by chemical and physicochemical means. Lipoprotein A represents the major family in high-density lipoprotein subfractions 2 and 3 and consists of two major nonidentical polypeptides, ApoAl and ApoII [2,6]. In addition, small amounts of a third apolipoprotein which probably also belongs to the lipoprotein A family could be found in subfraction 3 and was therefore designated as ApoAIII [7]. The protein part of lipoprotein B, the major family of low-density lipoprotein subfraction 3 has not been characterized entirely, and there seems to be some disagreement concerning the amount, type and molecular weight of the polypeptides found in this lipoprotein [8,9]. Apolipoprotein C, first demonstrated in very-low-density lipoprotein as a third class of apolipoproteins [lo], was found to be composed of four different polypeptides [ll]. These polypeptides, which w...

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“…This marked heterogeneity of HDL is mainly due to the well-documented occurrence of distinct, polydisperse families of lipoprotein particles of similar physical properties but different and specific apolipoprotein composition (1, 34-37). Albers and Aladjem (4) were the first to identify and separate by immunoprecipitation two major, discrete HDL particles, one of which contained apoA-I and apoA-I1 (LP-A-1:A-11) and the other only apoA-I (LP-A-I) as the integral protein constituents (4). This finding has been confirmed by several authors utilizing immunoafinity chromatography with polyclonal antisera to apoA-I and apoA-I1 as the procedure of choice for isolating LP-A-I and LP-A-1:A-II(5-10).…”

Section: Lipidlapolipoprotein Ratios Of Lp-a-i and Lp-a-i:a-iimentioning

confidence: 99%