title: The crystalline yolk-platelet proteins and their soluble plasma precursor in an amphibian, Xenopus laevis.
abstract: A single lipophosphoprotein complex, vitellogenin, was isolated and purified from the plasma of oestrogen-stimulated female toads by preparative ultracentrifugation and chromatography on TEAE-cellulose (triethylaminoethylcellulose). The protein contains 12% lipid, 1.5% phosphorus, 1.6% calcium and smaller amounts of carbohydrates and biliverdin. In amino acid composition it is identical with total yolk-platelet protein. The platelet protein, however, is fractionated on TEAE-cellulose into two components, a high-molecular-weight lipovitellin and a smaller phosvitin. Analyses of the soluble plasma vitellogenin suggest that it is a complex of two phosvitin molecules covalently bound to one lipovitellin dimer, and that it is the immediate precursor of the yolk proteins, into which it is converted by a molecular rearrangement. Uptake of vitellogenin from the plasma into the growing oocyte, and its subsequent crystallization as a yolk platelet, appear to be enhanced by gonadotrophic hormones.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001654:Bile Pigments / Q000032:analysis; D002118:Calcium / Q000032:analysis; D002852:Chromatography, Ion Exchange; D004589:Electrophoresis, Disc; D004625:Embryo, Nonmammalian / Q000032:analysis*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006062:Gonadotropins / Q000494:pharmacology; D008055:Lipids / Q000032:analysis; D008074:Lipoproteins / Q000096:biosynthesis / Q000097:blood* / Q000378:metabolism; D008297:Male; D010063:Ovum / Q000378:metabolism; D010750:Phosphoproteins / Q000032:analysis / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism; D010756:Phosphoric Acids / Q000097:blood*; D010758:Phosphorus / Q000032:analysis; D014176:Protein Biosynthesis; D011506:Proteins / Q000302:isolation & purification*; D014461:Ultracentrifugation; D014981:Xenopus
chemical_list: D000596:Amino Acids; D001654:Bile Pigments; D006062:Gonadotropins; D008055:Lipids; D008074:Lipoproteins; D010750:Phosphoproteins; D010756:Phosphoric Acids; D011506:Proteins; D010758:Phosphorus; D004958:Estradiol; D002118:Calcium