Oestrogen treatment has previously been shown to induce the formation of large amounts of a serum protein, vitellogenin (xenoprotein), in Xenopus laevis. Vitellogenin was purified from serum by dimethylformamide precipitation and was shown to be homogeneous by a variety of electrophoretic techniques. 2. The molecular weight of vitellogenin was estimated by gel filtration to be about 6x10(5). The chemical constituents of vitellogenin were determined and lead to the characterization of this protein as a serum calcium-binding glycolipophosphoprotein. 3. The extractable lipid accounted for 12% of vitellogenin. Gas-liquid-chromatographic analysis of the saponified lipid moiety showed the presence of palmitic acid, palmitoleic acid, stearic acid, oleic acid and linoleic acid in the molecular proportions 6.8: 1.5: 1.0: 3.6: 1.4. 4. The carbohydrate moiety consisted of 0.4g of hexose, 0.77g of hexosamine and 0.18g of sialic acid/100g of vitellogenin. 5. The calcium and phosphorus contents were 0.85 and 1.65g/100g of vitellogenin respectively. 6. Serum from oestrogen-treated animals injected with (45)CaCl(2) contained 9.7 times the radioactivity present in serum from untreated (45)CaCl(2)-injected animals. Of the radioactivity due to (45)CaCl(2) in the serum of oestrogen-treated animals 72% was non-diffusible on dialysis. Of this activity 65.4% was associated with the vitellogenin band on cellulose acetate electrophoresis.
