scholarly journals Lipid-protein globules of avian egg yolk. Isolation and properties of globules stable in concentrated sodium chloride solution

1977 ◽  
Vol 166 (3) ◽  
pp. 619-624 ◽  
Author(s):  
D V Vadehra ◽  
J M Bain ◽  
R W Burley
Keyword(s):  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Low Density Lipoprotein ◽  
Gel Filtration ◽  
Density Lipoprotein ◽  
Egg Yolk ◽  
Cholesteryl Esters ◽  
Yolk Globule ◽  
New Type ◽  
Globular Particle

A new type of globular particle, the ‘insoluble yolk globule’, was isolated from the egg yolk of three avian species (hen, duck, and emu) by centrifugation or gel-filtration chromatography. These globules are stable in NaCl and urea solutions at concentrations that dissolve or disrupt other constituents of yolk, The isolated globules are about 1% of the dry yolk of hen's and duck's eggs but about 8% emu's-egg yolk. Most of these globules are less than 2 micrometer in diameter. Electron micrographs of sections show a preponderance of globules in the range 0.125-0.25 micrometer, each with a thick shell surrounding a feature-less anterior. Globules with the same appearance were seen in sections of unfractionated yolk. Two kinds of larger particles were also observed: (i) particles with a distinct outer membrane and a vesiculated interior; (ii) featureless spheres, possibly of lipid. The insoluble yolk globules comprise protein (8-11% by dry wt.), phospholipid (31-35% total lipid), triacylglycerols (49-53%), cholesterol (8%) and cholesteryl esters (2-3%); the variations being among species. The phospholipid is accessible to phospholipase C. The isolated protein is heterogeneous and resembles the apoprotein from the yolk low-density lipoprotein.

scholarly journals Studies on the Apoproteins of the Major Lipoprotein of the Yolk of Hen's Eggs I. Isolation and Properties of the Low-molecular-weight Apoproteins

1975 ◽  
Vol 28 (2) ◽  
pp. 121 ◽  
Author(s):  
RW Burley
Keyword(s):  
Molecular Weight ◽  
Low Density Lipoprotein ◽  
Guanidine Hydrochloride ◽  
Gel Filtration ◽  
Density Lipoprotein ◽  
Egg Yolk ◽  
Soluble Form ◽  
Low Molecular Weight ◽  
High Lipid ◽  
Low Molecular Weight Proteins

In a continuing study of protein-lipid interactions in egg yolk, the total apoprotei.n mixture (i.e. the 'apovitellenins') from the high-lipid, low-density lipoprotein (density 0�97 gJml) of the yolk from hen's eggs has been isolated in a soluble form. By gel-filtration chromatography in 6M urea the mixture has been separated into several fractions from which three new low-molecular-weight proteins (I, la, and 11), making up about 30% of the total, have been isolated. The most plentiful of these (I) consists of stable aggregates with several identical subunits each of molecular weight about 10000. This protein is analogous to the principal protein from the corresponding lipoprotein of emu's egg yolk, i.e. emu's apovitellenin I. Hen's apovitellenin I has a slightly different amino acid composition from that of the emu; notably it contains a sulphydryl group. The hen's protein also forms more stable aggregates that are dissociated by detergent and by guanidine hydrochloride but are stable in urea.

Characterization of glycopeptides derived from the low-density lipoprotein of hen's egg yolk

1968 ◽  
Vol 46 (8) ◽  
pp. 983-988 ◽  
Author(s):  
J. Z. Augustyniak ◽  
W. G. Martin
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Egg Yolk ◽  
Low Density ◽  
Amide Nitrogen ◽  
Acetylneuraminic Acid ◽  
Hen’S Egg ◽  
Terminal Amino ◽  
Protein Moiety

Two glycopeptides (A and B) were isolated from pronase-digested vitellenin, the protein moiety of the low-density lipoprotein of hen's egg yolk. Aspartic acid was the only N-terminal amino acid of both glycopeptides but only A contained N-acetylneuraminic acid. A contained 55% hexose (mannose), 14% hexosamine, 12% N-acetylneuraminic acid, 0.71% amide nitrogen, and its molecular weight was 2.3 × 103. The corresponding values for B were 64, 17, 0.0, 0.75, and 2.0 × 103. Chemical analyses showed that B (and probably A) occurs in vitellenin with the heteropolysaccharide group bound N-glycosidically via the β-amide group of an asparaginyl residue. The indicated structure is R∙(NH)Asp∙Thr∙Ser∙(Ala, Gly, Val)∙Ile, where R, the heteropolysaccharide group, contains 2 hexosamine and 8 hexose residues.

scholarly journals Morphological characterization of the cholesteryl ester cycle in cultured mouse macrophage foam cells.

1983 ◽  
Vol 97 (4) ◽  
pp. 1156-1168 ◽  
Author(s):  
D J McGookey ◽  
R G Anderson
Keyword(s):  
Cholesteryl Ester ◽  
Lipase Activity ◽  
Lipid Droplets ◽  
Free Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
The Body ◽  
Cyclic Process ◽  
Low Density ◽  
Cholesteryl Esters

Mouse peritoneal macrophages can be induced to accumulate cholesteryl esters by incubating them in the presence of acetylated low density lipoprotein. The cholesteryl esters are sequestered in neutral lipid droplets that remain in the cell even when the acetylated low density lipoprotein is removed from the culture media. Previous biochemical studies have determined that the cholesterol component of cholesteryl ester droplets constantly turns over with a half time of 24 h by a cyclic process of de-esterification and re-esterification. We have used morphologic techniques to determine the spatial relationship of cholesteryl ester, free cholesterol, and lipase activity during normal turnover and when turnover is disrupted. Lipid droplets were surrounded by numerous 7.5-10.0-nm filaments; moreover, at focal sites on the margin of each droplet there were whorles of concentrically arranged membrane that penetrated the matrix. Histochemically detectable lipase activity was associated with these stacks of membrane. Using filipin as a light and electron microscopic probe for free cholesterol, we determined that a pool of free cholesterol was associated with each lipid droplet. Following incubation in the presence of the exogenous cholesterol acceptor, high density lipoprotein, the cholesteryl ester droplets disappeared and were replaced with lipid droplets of a different lipid composition. Inhibition of cholesterol esterification caused cholesteryl ester droplets to disappear and free cholesterol to accumulate in numerous myelin-like structures in the body of the cell.

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