Studies on phosphoproteins from fish eggs. I. Isolation and characterization of a phosphoprotein from the eggs of pacific herring.

1. A phosphoprotein containing 10.6% of phosphorus has been isolated from the eggs of Pacific herring by means of phenol extraction and DEAE-cellulose column chromatography. 2. Only 8 kinds of amino acid including a small amount each of the 2 kinds were detectable in the acid hydrolysate of the phosphoprotein. The protein contained only serine as hydroxyl group-bearing amino acid and this amino acid occupied more than 2/3 of total amino acid residues. No amino sugar was detectable. 3. A molecular weight of 4,200±400 was calculated from the sedimentation equilibrium data for the phosphoprotein. The following formula has been given tentatively for the protein on the basis of the molecular weight: (Lys)1(Arg)i(Asp)i(Phe)i(Leu)3(Ser)23_25(Phosphate)16. 4. The results of an alkali-catalyzed ^-elimination reaction suggested that all the phosphorus in the phosphoprotein are present in the form of monoesters linked to the hydroxyl groups of serine. 5. Two moles of DNP-group were introduced per 4,200 g of the protein. The Nterminal residue of the major component of the preparation was determined to be lysine by the analysis of DNP-products.