Apoproteins of avian very low density lipoprotein: demonstration of a single high molecular weight apoprotein

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Abstract
The high MW 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 MW apoprotein (apo-VLDL-B) as judged by electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate [SDS]. 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. Apo-VLDL-B can apparently be cleaved during VLDL isolation to produce an apparent heterogeneity of high MW apoproteins. The MW of plasma apo-VLDL-B was .apprx. 350,000. The protein was stable to reduction and S-carboxymethylation and showed no association with apo-VLDL-II through disulfide linkage. Apo-VLDL-B and apo-VLDL-II represented 54 and 46%, respectively, of the total VLDL protein recovered following gel filtration chromatography in SDS. Protein recovery in the chromatographic analyses (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-II monomer to apo-VLDL-B was .apprx. 32.