Effects of Phospholipids on the Conformation of Chicken High Density Lipoprotein

Abstract

Apolipoprotein A-I (apo-A-I), the major protein component of chicken high density lipoprotein (HDL), was isolated by hydrophobic interaction chromatography from the lipoprotein fraction of plasma. The apo-A-I was identified from its amino acid composition and molecular weight (by electrophoresis). The isolated protein contained 15% lipid, in the form of neutral lipids and free fatty acids, as compared with 50% lipid, including phospholipid, in intact HDL. The conformation of the isolated protein, as determined from the circular dichroism spectrum, was essentially that of the protein in intact chicken HDL, and similar to that of human HDL. The addition of phospholipid had little effect on the spectrum of this protein. Total delipidation of the protein by extraction with ethanol-diethyl ether mixtures removed the residual lipid, thereby producing an apoprotein with decreased helical structure. The secondary structure of this apoprotein could be restored by the addition of phospholipid.

Mobilization of ectopic yolk in Gallus domesticus: a novel reverse lipid transport process

“…ApoA1 is also found on the surface of mammalian HDL in addition to ApoE. Although previous studies have indicated that ApoA1 is expressed in a variety of tissues in the chicken, including hepatocytes, intestinal cells, adipocytes and myocytes (Blue et al, 1982;Shackelford and Lebherz, 1983;Rajavashisth et al, 1987;Brown, 1989), this is the first report showing ApoA1 expression in macrophages. Intriguingly, as ApoA1 is the only apolipoprotein required for HDL formation in chickens, the possibility that chicken macrophages have the unique ability to produce HDL precursors in order to mediate lipid efflux cannot be ruled out.…”

“…Birds transport large quantities of yolk during several periods of their life history: in ovo and during the early post-hatching period, during the active egg-laying cycle when eggs are being formed, and during follicular atresia (Shackelford and Lebherz, 1983;Rajavashisth et al, 1987;Brown, 1989;Barron et al, 1999). During follicular atresia, large yolk-filled follicles involute and yolk lipid is extruded into the abdominal cavity.…”