PAPER ELEGTROPHORETIC CHARACTERIZATION OF PROTEINS AND LIPOPROTEINS OF HEN'S EGG YOLK

Abstract

Staining for ester-linked protein phosphorus (ELPP) gave positive reactions with both of the main lipoprotein zones (P-1 and P-2) of paper electropherograms of egg yolk in certain buffers, including veronal buffer, pH 8.6. Treatment of the yolk with 1.0 M NaCl or with complexing agents (ethylenediaminetetraacetate, veronal–citrate buffer) resulted in the appearance of larger amounts of ELPP in the phosvitin (PT) zone. The distribution of the livetin zones suggested that the lipoprotein zone P-1 overlapped the greater part of the γ-livetin zone. This suggestion was supported by the results of immunoelectrophoretic experiments.Yolks in which the phosphorus had been labelled with P³²were separated by ultracentrifugation into (a) granule material; (b) low density fraction (LDF); and (c) the soluble livetin fraction. Paper electrophoretic studies of whole egg yolk and of these preparations showed (a) that the P-1 zone of electropherograms of whole egg yolk in veronal buffer comprised all of the LDF plus most of the γ-livetin plus a proportion of the phosvitin that depended on the strength of the salt solution used to disperse the yolk, the nature of the buffer, and the absence or presence of complexing agents; and (b) that the P-2 zone comprised the lipovitellin fraction together with more or less of the phosvitin. Dispersion of the yolk in 1.0 M NaCl, pretreatment of the yolk with ethylenediaminetetraacetate, or use of veronal–citrate buffer led to the appearance of relatively high proportions of the total protein-bound phosphorus and P³²in the 'fast' phosvitin (PT) zone.