ATLANTIC HALIBUT (HIPPOGLOSSUS-HIPPOGLOSSUS) VITELLOGENIN - INDUCTION, ISOLATION AND PARTIAL CHARACTERIZATION

Vitellogenin (VTG) synthesis was induced by repeated injections of est radiol-17 beta in juvenile Atlantic halibut (Hippoglossus hippoglossus ). VTG eluted as a large, phosphoprotein containing peak on DEAE-Sepha cel chromatography of plasma from estradiol-17 beta treated juvenile a nd mature female, but not mature male halibut. A purification procedur e for Atlantic halibut VTG was developed, where VTG was precipitated w ith MgCl2, EDTA and distilled water, and the precipitated protein subm itted to anion exchange chromatography on DEAE-Sephacel. Precipitated VTG eluted as a broad, partly dissociated peak on DEAE-Sephacel, when chromatography was run at 4 degrees C, but the protein appeared intact when analysed both by SDS PAGE and native PAGE. DEAE-Sephacel chromat ography at room temperature resulted in an irregular elution pattern a nd a dissociated protein fraction, as analysed by SDS PAGE. Biochemica l characterization of VTG showed that the molecular mass of the monome r was ca 160 kDa, as estimated by SDS-PAGE. The total lipid content wa s 19.8% w/w, with 64%, or 12.7% of the total weight, as phospholipid. Protein bound phosphorus constituted 0.62% w/w of halibut VTG. Plasma dilution curves from mature and maturing female halibut were parallel with a dilution curve from halibut egg yolk homogenate in an homologou s RIA. Plasma from mature male, but not juvenile halibut crossreacted with the VTG antiserum.