Characterization of apolipoproteins from chicken plasma

Although functionally similar, the lipoprotein systems of birds and mammals differ in composition. The major apolipoproteins, apo A-I and apo B, are common to all vertebrates; however apo A-II and apo E, functionally important components of mammalian lipoproteins, are absent from chicken plasma. Chicken apo A-I and apo B have been characterized, and several minor apolipoprotein components have been observed in electrophoretic patterns of chicken lipoproteins. In this study a single density gradient ultracentrifugation was used to isolate and subfractionate chicken lipoproteins into density classes. Isolated lipoproteins were delipidated with hexane-isopropanol (3:2). Apolipoproteins were then solubilized at pH 8.5 in 3 M guanidine hydrochloride and chromatographed on a 25 X 0.4 cm C4 reversed-phase column using 0.1% trifluoroacetic acid in a gradient of acetonitrile in water. Molecular weights estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino acid compositions were compared with those of apolipoproteins from other species in a search for functional similarities. Similarities in composition between the major chicken apolipoprotein and several human apolipoproteins were observed.