Study On Proteinaceous Infectious Agent In Cultured Marine Fishes

Proteinaceous infectious agent ( prion ), which is normally pointed as the aggregate of prion protein, is protein only and causing agents of transmissible spongiform encephalopathies ( TSE ). PrP has a large diversity and a wide range of distribution. It is highly possible that prion and TSE could form in cultured fishes through forage. Therefore, it is of great importance to select cultured Japanese sea bass and bastard halibut , which are two most important cultured species , as the research model to study the PrP encoding gene structure and the tissue expression. Through a series of experiments, the following results were received:The prion protein encoding gene sequences of Japanese sea bass ( Lateolabrax japonics) and bastard halibut(Paralichthys olivaceus) were cloned and analyzed. Data show that the PrP of Japanese sea bass consists of 507 amino acid residues, weighing about 54kilodaltons, and the pI is about 9.07; while the PrP of bastard halibut consists of 497 amino acid residues, weighing 52 kilodaltons, and the pI is about p.07. Furthermore, sequences analysis also demonstrate that these two PrPC bear the structural signatures of PrP including a signal sequence, basic structure, tandem repeats, a hydrophobic region, a glycosylation site, a disulphide bridge and a glycosylphosphatidylinositol anchor site. The homologue of the sequence of sea bass and bastard halibut to pufferfish, zebra fish and Atlantic salmon ranged differently from 28% to 68%。The homologue between sea bass and bastard halibut is 68.4%. The homologue between sea bass and bastard halibut in the amino acids of Hydrophobic region is 72.2% with the homologue of 77.9% in the nucleotide sequence. Summarily, the analysis of sequence homologue in amino acid and nucleotide sequences showed that there is little possibility that the TSE can be mutually between mammals and fish.The sequencing results of the genome of PrPC indicated that the PrPC is encoded by a single exon in flounder .A 616bp-long fragment of 5'flanking region of PrPC...