RESUMEN
In oviparous organisms, yolk accumulation in the oocytes is critical and indispensable for the development of the newly hatched young ones. In fish and many other oviparous vertebrates, the major constituents of the egg-yolk are synthesized as a precursor in the liver. The precursor is transported to the oocyte for uptake and cleaved into major yolk proteins lipovitellin, phosvitin and β’-components. The eggs of Channa punctatus are pelagic, have large oil globule and exceptionally high lipid content. Lipovitellin was isolated by single step gel filtration chromatography on Sepharose 6B. Purified native lipovitellin showed immunological reactivity with vitellogenin antiserum. Phosvitin isolated by phenol extraction method could not be visualized with routine protein staining methods, whereas incorporation of trivalent ions in the coomassie brilliant blue stained phosvitin. It was characterized by in vivo labeling of egg-yolk proteins with 32P. The molecular mass of murrel phosvitin was less than 14,000 kDa.
RESUMEN
Plasma from estrogenized, [32P] NaH2PO4-injected murrel, Channa punctatus was collected in the presence of proteolytic inhibitors and subjected to different separation procedures singly or in combination, viz., gel filtration chromatography on Ultrogel AcA 34, ion-exchange chromatography on DEAE sephacel, or selective precipitation with dimethylformamide or with Mg2+: EDTA in order to isolate vitellogenin from other plasma proteins. The results show that chromatography on Ultrogel or DEAE sephacel yields intact vitellogenin whereas prior precipitation with DMF or with Mg2+: EDTA results in either co-precipitation of other plasma proteins or in the cleavage of phosvitin-like material from the native vitellogenin molecule.