Expression of the amino terminal part of synthetic human growth hormone gene and somatomedin-like activity of expressed protein

We have constructed three different plasmids containing partsof the human growth hormone gene using chemically synthesizedoligomers and cloned them for the purpose of expressing themin Escherichia coli. AB, B and BC gene segments correspondingto ABhGH (residue 1–138), BhGH (residue 44–138)and BChGH (residue 44–192) were placed under the controlof a tryptophan promoter in the expression vector. Upon inductionwith 3-indolylacrylic acid, ABhGH accumulated in cells but theBhGH and BChGH segments were not detected appreciably. Northernblotting analysis showed that the amount of mRNA transcribedfrom the AB gene segment was about ten-fold higher than thatfrom the B or BC gene segment. ABhGH was found to have insulin-likegrowth factor I (IGF-I) activity, which could be explained bythe hydrophilicity curves of these proteins.