High-density Lipoprotein Species Research Articles

Characterization of the high-density lipoprotein and its major apoprotein from human, canine, bovine and chicken plasma

The high-density lipoproteins (HDL) from canine, bovine, and chicken plasma have been shown to contain almost exclusively the apolipoprotein A-I, while human HDL contains a second major component, the apolipoprotein A-II. Chemical cross-linking demonstrated that dog and chicken HDL contain three apolipoprotein A-I molecules per particle, while bovine HDL contain approximately six apolipoprotein A-I molecules per particle. By this method, the amount of protein in human HDL2 (d = 1.063–1.12) was found to be approximately 120000 g/mol, while for human HDL3 (d = 1.12–1.21) a value of approximately 90000 g/mol was obtained, suggesting that the protein complement of HDL2 and HDL3 differ by only one apolipoprotein A-I chain per particle. Comparison of the apolipoprotein A-I from various animal species indicated that the canine and human apolipoprotein A-I proteins were the most similar by fluorescence, self-association properties, and immunoreactivity. Cross-linking of chicken and bovine apolipoprotein A-I yielded patterns distinctly different from that obtained with the human or canine counterpart. It is concluded that the quaternary structure of the various species of HDL is not directly correlated with the degree of self-association found for the protein constituents.

Dissociation of apolipoprotein A-I from porcine and bovine high density lipoproteins by guanidine hydrochloride

Dissociation of apolipoprotein A-I from pig and steer high density lipoproteins (HDL) deficient in apoA-II was determined by exposing native HDL fractions to 6 M guanidine hydrochloride (Gdn-HCl) at 37°C for periods from 5 min to 18 h. Bovine high density lipoprotein (HDL-B) was isolated at d 1.063–1.100 g/ ml while porcine high density lipoprotein (HDL-P) was isolated at d 1.125–1.21 g/ ml. Incubation for 5 min with Gdn-HCl resulted in a 45 and 3% loss of apoA-I from HDL-P and HDL-B, respectively. Exposure to the denaturant for 3 h resulted in a 75% loss of apoA-I from HDL-P and a 30% loss from HDL-B. Analytic ultracentrifugation patterns paralleled the degree of apoA-I dissociation from each HDL species. The initial flotation peak for HDLP shifted from F° 1.20 2.68 to F° 1.20 10.75 after 3 h exposure while HDL-B showed only a small shift from F° 1.20 8.30 to F° 1.20 8.96 after 3 h exposure. HDL-P particle diameter increased 25% after 5 min of Gdn-HCl treatment and large, flattened structures predominated after 3 h. There was no change in the size of HDL-B after 5 min exposure and only 16% increase in particle diameter after 3 h. The difference in behavior of HDL-B and HDL-P to Gdn-HCl exposure is discussed in terms of differences in apolipoprotein A-I amino acid composition, interaction of apolipoprotein A-I with phospholipids and the possible involvement of the cholesteryl ester core.