Two Low-molecular-weight Apoproteins (Apovitellenins I and II) from a Lipoprotein of Goose?s Egg Yolk: A Comparison with Related Species

Abstract

As part of a comparative study of egg yolk from different avian species, the major lipoprotein and its mixed apoproteins from the egg yolk of the chinese goose (Anser cygnoides) have been prepared. From the apoprotein mixture, two new proteins, of molecular weight approximately 10000 and 22000 according to gel electrophoresis in detergent, have been isolated by gel-filtration chromato-graphy in urea. The protein of lower molecular weight corresponds in amino acid sequence to apovitellenin I, a protein previously isolated from other avian species. As a comparison with other members of the same avian family (Anatidae), the amino acid sequence of apovitellenin I from the pekin duck (Anas platyrhynchos) was re-investigated and that of the muscovy duck (Cairina moschata) investigated. These were found to be identical to the sequence of goose's apovitellenin I. The second new protein is similar in composition, molecular weight, and solubility to apovitellenin II, a protein present in small amount in hen's egg yolk. A protein corresponding to apovitellenin II could not, however, be detected in the egg yolk of either species of duck.