APOPROTEINS OF AVIAN VERY LOW-DENSITY LIPOPROTEIN - DEMONSTRATION OF A SINGLE HIGH MOLECULAR-WEIGHT APOPROTEIN

The high molecular weight apoproteins of very low density lipoprotein (VLDL) were compared after preparation of VLDL from plasma and sera of diethylstilbestrol-treated roosters. When prepared from plasma with adequate control of endogenous proteolytic activity, VLDL contained a single high molecular weight apoprotein (apo-VLDL-B) as judged by electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate. Serum VLDL contained multiple apoprotein species, the largest of which corresponded to apo-VLDL-B. Immunological analyses showed that the multiple apoproteins of serum VLDL were quantitatively and qualitatively indistinguishable from plasma apo-VLDL-B. These data indicate that apo-VLDL-B can be cleaved during VLDL isolation to produce an apparent heterogeneity of high molecular weight apoproteins. The molecular weight of plasma apo-VLDL-B was estimated to be 350000. This protein was stable to reduction and S-carboxymethylation and showed no association with apo-VLDL-II [Chan, L., Jackson, R. L., O'Malley, B. W., & Means, A. R. (1976) J. Clin. Invest. 58, 368] through disulfide linkage. Apo-VLDL-B and apo-VLDL-II represente d54% and 46%, respectively, of the total VLDL protein recovered following gel filtration chromatography in sodium dodecyl sulfate. Protein recovery in the chromatographicanalyses (92%) was sufficient to conclude that apo-VLDL-B and apo-VLDL-II are the major and possibly the only apoproteins of chicken VLDL. The molar ratio of the apo VLDL-IImonomer to apo-VLDL-B was estimated to be 32. © 1979, American Chemical Society. All rights reserved.