OVALBUMIN AND OTHER WATER-SOLUBLE PROTEINS IN AVIAN YOLK DURING EMBRYOGENESIS

Abstract

The proportion of water-soluble protein in egg yolk increased markedly after 12 days' incubation, concurrent with the appearance of a new fraction that evidently entered from the egg white. The electrophoretic, sedimentation [Formula: see text], molecular weight (45 × 103), and chromatographic properties of this new fraction, after 18 days' incubation, were the same as, and the tyrosine–tryptophane and phosphorus–nitrogen ratios were similar to those of authentic ovalbumin. Ovalbumin is known to have two components differing in phosphorus content and both were evident in the authentic sample and in the new yolk fraction. At the later stages of incubation the ovalbumin component of lowest phosphorus content predominated and this also may be the form that was present in the serum of the embryo. Changes in the other components of the water-soluble material during embryogenesis were less dramatic. Chromatography on DEAE-cellulose revealed at least nine yolk components in unincubated egg, although only the three livetins were made evident by free-boundary electrophoresis. The great increase in ovalbumin prevented detection of changes in the livetins during embryogenesis but α-livetin (serum albumin) apparently disappeared most rapidly and completely.