cDNA Cloning, Structure Analysis and Protein Synthesis in Escherichia coli of Fish Growth Hormones Participating in the Growth and Seawater Adaptation of Teleosts

Abstract

Growth hormone (GH) is now considered to be involved in the mechanism of seawater adaptation as well as in the growth-promoting reaction in teleosts. In an effort to elucidate the reaction mechanisms of GH in the osmoregulation and growth promotion, we have cloned and analyzed the cDNAs of yellowtail, hard tail and flounder GHs. The deduced mature yellowtail, hard tail and flounder GHs are composed of 187, 188 and 173 amino acid residues, respectively. These and other GHs are found to conserve 5 GH-specific domains, GD1 to GD5. In the teleost GHs, the GD5 is particularly highly conserved, suggesting the specific role of this domain in these GHs. Flounder GH, which has the smallest molecule ever found, lacks an extra region of these GD domains.
To study the biological activities of teleost GHs, we have synthesized recombinant yellowtail and flounder GHs by E. coli expression vectors. Synthesized GHs have been purified and folded in glutathione red/ox buffer, and both recombinant GHs exhibited full growth-promoting activities on rainbow trout fries.