Growth-promoting activity of tuna growth hormone and expression of tuna growth hormone cDNA in Escherichia coli

Tuna (Thunnus thynnus) growth hormone (GH) was purified by using a column of Sepharose 4B to which tuna GH-specific IgG was linked. The molecular weight and isoelectric point of tuna GH were 21,000 and 6.5, respectively. The growth of snapper (Pagrus major) was remarkably accelerated when the purified hormone was administered by four intraperitonial injections at intervals of 5 days: 1.5-fold in length and 1.9-fold in body weight/60 days. To produce tuna GH in Escherichia coli cells, expression plasmids pTES8 and pTES8S for tuna GH cDNA with or without the signal peptide region were constructed and GH production in E. coli cells was examined with the Maxicell system. The product specified by the plasmids in E. coli cells was immunologically identified to be tuna GH.