Purification and characterization of the female-specific protein (vitellogenin) in mature female hemolymph of the prawn,Penaeus monodon

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Abstract
Purifying and characterizing the female-specific protein (vitellogenin) from the hemolymph of mature female prawn, Penaeus monodon, were the objectives of this study. Hemolymph was stained with Sudan Black B and fractionated by an ultracentrifuge. A specific protein (vitellogenin) appeared in the fourth fraction of the female hemolymph based on the Western blotting and polyacrylamide gel electrophoresis (PAGE). The fourth fraction of the female hemolymph was further purified by PAGE and electro-elution. A purified vitellogenin was obtained according to the PAGE. Two polypeptide subunits (170 kD and 82 kD) were detected in the SDS-PAGE. The purified vitellogenin could be stained with Sudan Black B and periodic acid-Schiffs reagents and further considered as a lip-glyco-phosphoprotein. Amino acid composition was also characterized in the purified vitellogenin of P. monodon after acid hydrolysis. High levels of glutamic acid, aspartic acid and glycine were detected. Cysteine was undetected. Non-disulfide bonds were found to exist between the binding of polypeptide subunits. The difference of the number of polypeptide subunits and amino acid composition was also compared between the purified vitellogenin and vitellin of P. monodon. The biochemical characters suggest that vitellogenin in hemolymph is incorporated into oocytes and then dissociated into two subunits. One of the subunits (170 kD) was partially digested and transformed into vitellin in combination with another subunit (82 kD).