Structure of egg yolk very low density lipoprotein. Polydispersity of the very low density lipoprotein and the role of lipovitellenin in the structure

Abstract

Egg yolk very low density lipoprotein contained on the average 75% of lipid which could be extracted by ether and 25% of a residual lipoprotein, the classical lipovitellenin. The ether-extracted lipid was composed of 75% triglycerides, 7% sterols, 2% mono- and diglycerides, and 16% phospholipids. Lipovitellenin contained 48% lipid composed of 87% phospholipids, 11% triglycerides, and 2% sterols. The protein vitellenin was composed for the most part of units of 74,000 and 270,000 daltons molecular weight. Egg yolk very low density lipoprotein is polydisperse. Preparative ultracentrifugation separated it into six fractions of different average molecular size, and gel chromatography separated it into five. The fractions of larger molecular size contained more lipid and triglyceride than did the fractions of smaller molecular size. The proteins of the fractions appeared to be similar. Egg yolk very low density lipoproteins appear to be a series of molecules composed of cores of lipid of varying sizes with each core surrounded by a layer of lipovitellenin, which is composed principally of glycoprotein and phospholipid.