Studies on the Protein Composition of Human Serum Very Low Density Lipoproteins: Demonstration of theβ2-Glycoprotein-I

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Abstract
Human serum VLDL [very low density lipoprotein] isolated by polyanion precipitation and ultracentrifugation were delipidated with ethanol/diethyl ether. By electrophoresis in 10% polyacrylamide gels containing 8 M urea, a protein was found which co-migrated with apolipoprotein E. This protein was purified by column chromatography and turned out to be identical with .beta.2-glycoprotein-I, the serum factor which is necessary for the precipitation of triglyceride-rich lipoproteins with sodium decyl sulfate or sodium dodecyl sulfate. Upon analytical isoelectric focusing, .beta.2-glycoprotein-I gave 4 major bands in the pH region 5.7-6.6. All 4 bands gave an immunochemical reaction of identity with a monospecific antiserum. From its unique amino acid composition it was concluded that .beta.2-glycoprotein-I is distinct from all apolipoproteins described previously in the literature.