Studies of the proteins in human plasma very low density lipoproteins.

The protein components of human plasma very low density lipoproteins (Sf > 20) were studied following partial and total delipidation. After the neutral lipids were extracted with heptane, the resulting phospholipid-protein complexes contained at least one immunochemical reactant different from the major apoproteins of high density and low density lipoproteins. Purification required total delipidation with ethanol-ether, gel filtration, and diethylaminoethyl cellulose chromatography. Two proteins were then isolated that differed from the proteins of high density or low density lipoproteins, and their purity was established by immunochemical analysis and polyacrylamide gel electrophoresis. One of these had y mobility, NHz-terminal threonine, COOH-terminal valine, and no tyrosine, histidine, cysteine, or cystine. The second, az-migrating protein had NH2terminal serine, COOH-terminal alanine, and no isoleucine, cysteine, or cystine. These two proteins constituted approximately half of the total protein in very low density lipoprotein.