Studies on pig serum lipoproteins. III. Affinity chromatography of native lipoproteins on concanavalin A-sepharose

The comparison of the binding capacities of the three major classes of pig serum lipoproteins, very low-density, low-density and high-density lipoproteins, to concanavalin A, was demonstrated by affinity chromatography on concanavalin A-Sepharose. Very low-density lipoprotein was separated into two fractions (60 to 66% of total protein was adsorbed). Each fraction had different electrophoretic mobility in pore size gradient gel. The majority of the carbohydrate was found in the adsorbed fraction. The carbohydrate content of the unadsorbed fraction was 0.14% sialic acid. 0.47% hexosamine and 0.93% neutral sugars, and of the adsorbed fraction, 2.05, 3.21 and 4.20%, respectively. The adsorbed and unadsorbed fractions contained fucose, mannose and galactose in the molar ratio of 1.0 : 3.6 +/- 0.2 : 2.2 +/- 0.4 and 1.0 : 3.1 +/- 0.2 : 2.5 +/- 0.3, respectively. Based on these results, two different molecular species were proved to be present in very low-density lipoproteins. In high-density lipoproteins, 80 to 85% of the total protein was not adsorbed on concanavalin A-Sepharose in spite of the presence of mannose in the apoprotein. In contrast to these lipoproteins, low-density lipoprotein was completely adsorbed on concanavalin A-Sepharose. However, the separation of the subfractions of low-density lipoprotein as well as the subfractions of high-density lipoprotein could not be achieved by this affinity column. The carbohydrate content of eluted fractions of low-density and high-density lipoproteins was identical with the previously reported values obtained in native lipoproteins. This difference in affinities for concanavalin A was also evidenced by gel electrophoretic profiles in urea and in sodium dodecyl sulfate which showed different glycoprotein distribution in each class of lipoproteins.