Properties of rooster serum high density lipoproteins

Abstract

The physical and chemical properties of normolipemic rooster serum high density lipoproteins (HDL) were determined and compared with human HDL. Rooster HDL was found to be composed of essentially one class of particles, as determined by flotational analysis at d 1.21 g/ml in the analytical ultracentrifuge. On a weight-percentage basis, it contained 44, 29, 16, 5 and 6% protein, phospholipid, cholesteryl ester, cholesterol, and triacylglycerol, respectively. This distribution resembled that of human HDL 2 more closely than that of HDL 3. On the other hand, the physical parameters of rooster HDL resembled those of human HDL 3. The sedimentation coefficient, diffusion coefficient, molecular weight, partial specific volume and the anhydrous frictional ratio for rooster HDL were 3.99 S 4.36 · 10 −7 cm 2 · s −2, 1.73 · 10 5,0.868 ml/g, and 1.24, respectively. However, the circular dichroic spectra of rooster HDL indicated an α-helical content 20% greater than that in human HDL. The lipid composition resembled that of human HDL except for a relatively higher content of stearic acid. The HDL protein gave several bands by polyacrylamide gel electrophoresis. The main component, representing almost 90% of the total protein, had a molecular weight of about 26 000, an amino acid composition and an electro phoretic mobility similar to those of human apolipoprotein A-I. A component of mol. wt 15 000 and a group of fast-migrating peptides, resembling the human apo C peptides, were also found. It is concluded that the structure of rooster HDL, although showing similarities to human HDL, can be distinguished from the latter by some physical parameters, but particularly by its polypeptide distribution.