EXPRESSION OF CHINOOK SALMON GROWTH-HORMONE GENE IN ESCHERICHIA-COLI

To achieve a high level of expression in E. coli, the cDNA of chinook salmon gro-th hormone (sGH) was modified by the removal of a 5' nontra nslated sequence, as well as the sequence that specified the signal pe ptide of pregrowth hormone and by the introduction of restriction site sequences and the ATG initiation code into the DNA sequence coding fo r mature sGH by polymerase chain reaction (PCR). PCR was carried out i n which a set of primers was chosen by attaching the EcoRI sequence an d ATG codon to the 5' end of the start primer and the BamHI sequence t o the 5' end of the halt primer. After restriction digestion and ligat ion, the modified sequence was into the expression vector of pKK 223-3 using trp and lac promoters. In the presence of isopropyl-beta-D-thio galactopyranoside (IPTG) mature sGH, a single polypeptide of molecular weight 22 000, was identified by Coomassie blue staining of NaDodSO4- polyacrylamide gel of total protein from transformed E. coli cells, an d by reaction with salmon GH antiserum.