Syntheses of recombinant yellowtail and flounder growth hormones in Escherichia coli.

For syntheses of recombinant yellowtail and flounder growth hormones (r-yGH and r-fGH) in E. coli, expression plasmids were constructed. The expression level of r-yGH and r-fGH in the host cells were very high, reaching 15 and 8% of the total protein, respectively. These product proteins were accumulated in inclusion bodies in the cells. The recombinant hormones were isolated from the pellets ina glutathione reduction/oxidation buffer. The refolded hormones were further purified by DEAE-Toyopearl 650M chromatography to homogeneity. The purified r-yGH and r-fGH were composed of 188 and 174 amino acid residues, respectively, having amino-terminal sequences starting with methionine. The recombinant hormones had potent growth-promoting activities on juvenile rainbow trout Salmo gairdneri in a dose-dependent manner.