A full-length cDNA encoding translationally controlled tumor protein of marine flatfish turbot （Scophthalmus maximus）, SmTCTP, was isolated with rapid amplification of cDNA Ends （RACE）. SmTCTP consisted of a 5＇ untranslated region （UTR） of 84 bp, a 3＇ UTR of 451 bp and an open reading frame （ORF） of 513 bp, encoding a protein of 170 amino acid residues, which contained two signature sequences of TCTP family. The 5＇UTR of SmTCTP started with a 5＇-terminal oligopyrimidine tract （5＇-TOP）, a typical feature for translationally controlled mRNAs. The deduced amino acid sequence of SmTCTP was similar to the other known vertebrate TCTPs in a range of 58.8% to 64.1%. The length of fish TCTPs was diverse among species, e.g., TCTP of turbot and sea perch （Lateolabraxjaponicus） is 170 aa in length, while that of zebrafish （Danio rerio） and rohu （Labeo rohita） is 171 aa in length. Northern blot analysis revealed that SmTCTP has only one type of mRNA. Its expression level in albino skin was slightly higher than that in normal skin. We constructed the pET3Oa-SmTCTP expression plasmid. The recombinant protein of His-tag SmTCTP was over-expressed in E. coli, purified and identified with peptide mass fingerprinting. These results may pave the way of further investigation of the biological function of TCTP in fish.
WANG Jian GUO Huarong ZHANG Shicui YIN Licheng GUO Bin WANG Shaojie
The toxic mechanism of herbicide butachlor to induce extremely high lethality in marine flatfish flounder, Paralichthys Olivaceus, was analyzed by histopathological examination, antioxidant enzymes activities and ATP content assay. Histopathological examination of gill, liver and kidney of exposed fishes showed that gill was a target organ of butachlor. The butachlor seriously impaired the respiration of gills by a series of lesions such as edema, lifting and detachment of lamellar epithelium, breakdown of pillar cells, and blood congestion. The dysfunction of gill respiration caused suffocation to the exposed flounder with extremely high acute lethality. Antioxidant enzyme activity assay of the in vitro cultured flounder gill （FG） ceils exposed to butachlor indicated that butachlor markedly inhibited the antioxidant enzyme activities of Superoxide dismutase （SOD）, catalase （CAT） and glutathione peroxidase （GPX）. Furthermore, along with the decline of antioxidant enzyme activities, ATP content in the exposed FG cells decreased, too. This infers that the oxidative stress induced by butachlor can inhibit the production of cellular ATP. Similar decrease of ATP content was also observed in the exposed flounder gill tissues. Taken together, as in FG cells, butachlor possibly induced a short supply of ATP in pillar cells by inhibiting the antioxidant enzyme activities and then affecting the contractibility of the pillar cells, which in turn resulted in the blood congestion and suffocation of exposed flounder.
