FRACTIONATION AND DISSOCIATION OF THE AVIAN LIPOVITELLINS AND THEIR INTERACTION WITH PHOSVITIN

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Abstract
Phosvitin and lipovitellin, the granule proteins of hen's egg yolk, were clearly separated by gradient elution on Dowex-1 columns. No phosvitin could be detected in the lipovitellin fraction but the first eluates of the phosvitin fraction contained lipovitellin of high protein phosphorus content. These initial eluates contained only two components sedimenting at rates slightly higher than dimer and monomer lipovitellin. As the lipovitellin monomer does not ordinarily occur in neutral solvents, the slower sedimenting material is either a new component or the monomer stabilized through interaction with phosvitin.Gradient elution chromatography of the total lipovitellins on hydroxyapatite showed that β-lipovitellin was completely eluted by 0.6 M phosphate buffer at pH 6.8 and appeared to be homogeneous. However, α-lipovitellin was heterogeneous: it was eluted over a concentration range of 0.7 to 1.4 M and the protein phosphorus content and dissociative behavior of successive fractions showed a progressive change with increasing ionic strength. Superimposed on this general heterogeneity of α-lipovitellin, there was consistent evidence of two poorly defined components, and three when the α-fraction was rechromatographed. Following dissociation and reassociation, there was no evidence of hybridization between monomers of α- and β-lipovitellin. Changes in the chromatographic patterns of α-lipovitellin following dissociation may indicate hybridization of different α-monomers, but these could also arise from structural changes in the monomers.