| Vitellin (Vn), the major egg yolk protein synthesized in female shrimp during gonad maturation, provides nourishing substance to the growing and developing of embryo and larva. Biochemical character of Vn and its precursor vitellogenin (Vg) from Chinese shrimp were studied and a full-length cDNA of Vg was cloned.Vn and Vg were isolatied from female shrimp with gel filtration chromatography (SephadexG-150), ion exchange chromatography (DEAE-Cellulose-32) and electroelution methods jointly. Vn is a lipo-glyco-phospho-caroprotein with an apparent molecular weight of 409 ku, whose pâ… is 5.4. The molecule of Vn contains 8.7% oligosaccharide. Five subunits(202 ku,171 ku,105 ku,80 ku and 73 ku) and one disulfide bond were detected. Vg is a lipo-glyco-phospho-caroprotein too. Its molecular weight is 476 ku, pâ… is 5.2. About 11.6% oligosaccharide was detected in the whole Vg molecule. Nondisulfide bond was found in the binding of polypeptide subunits.Antiserum was gained from a rabbit with purified Vn as antigen, which can be used to detect Vn or Vg of shrimp from the identical genus but not from other genus of crustacean. It was proved with immunohistochemical methods that extraovarian original Vg is synthesized in hepatopancreas and secreted into hemolymph. Vg is absorbed by follicular cells from hemolymph and then transferred into oocytes where Vg is made into Vn. ELISA was introduced to detect the change of Vn content in the eggs and larva of different stage. The content of Vn decrease along with the development of larval prawn, Vn is digested very quickly from N3-4 to N5-6 and from N5-6 to Z1, the decrease of Vn are 1322 ng/mL and 1213 ng/mL, it occupy gross of Vn content of eggs 38.9% and 35.7%, respectively. After the stage of Z1, the content of Vn was not detected.In the present study, a full-length cDNA sequence encoding Vg was cloned by homologous clone and RACE method from mature ovary of Chinese shrimp Fenneropenaeus chinensis, an important commercial species in aquaculture. This cDNA sequence is 7956 bp in length, containing a 7761 bp open reading frame, which encodes 2587 amino acid residues. The deduced amino acid sequence showed 80-95% identity with other known crustacean Vgs. Multiple alignment of amino acid sequences of Vgs from different crustaceans shows that Vg of F. chinensis possesses the highest identity with that of F. merguiensis. Deduced Vg contains a putative N-terminal signal sequence (1-18) followed by a mature peptide including 2569 amino acid residues. A potential cleavage site (RXRR) that is recognized by subtilisin-like endoproteases was identified in the deduced Vg precursor. The deduced peptide, with a predicted molecular weight of 282 ku, and a pâ… of 6.13, has more negatively charged amino acids. Vg contains more alanine, glutamic acid, valine and isoleucine (Ala 11.56%, Glu 8.99%, Val 8.52% and Ile 7.12%) by amino acids composition analysis. Vg gene was detected both in female and male shrimp by RT-PCR method. But transcriptions happen exceptionally in ovary and hepatopancreas of vitellogensis females.
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